Liquid crystal display device

ABSTRACT

A substrate for a liquid crystal display including a plurality of gate bus lines and a plurality of data bus lines that cross the gate bus lines, as well as a thin film transistor connected to one of the data bus lines. The display also includes a first electrode with a body portion and a plurality of branches extending from the body portion, wherein at least some of the branches include a first branch portion, which extends from the body portion and defines a first angle, and a second branch portion, which extends from the first branch portion, and which defines a second angle. The first angle is greater than said second angle, and both angles are between 0° and 90° Also included is a second electrode that overlaps at least a portion of the first electrode, and an insulation film between the first and second electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of Application Ser. No. 12/723,977,filed Mar. 15, 2010, which is a Divisional of application Ser. No.11/104,309, filed Apr. 12, 2005, now U.S. Pat. No. 7,710,523, issued May4, 2010, which claims priority of Japanese Patent Application No.2005-001356, filed on Jan. 6, 2005, the contents being incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a MVA (Multi-domain Vertical Alignment)mode liquid crystal display device, and particularly to a liquid crystaldisplay device in which a polymer for determining a direction in whichliquid crystal molecules tilt while voltage is being applied is formedin a liquid crystal layer thereof.

2. Description of the Prior Art

In general, a liquid crystal display device is constituted of: a liquidcrystal panel which is fabricated to contain liquid crystal between twosubstrates thereof; and polarizing plates which are arrangedrespectively in the two sides of the liquid crystal panel. A pictureelement electrode is formed in each of picture elements in one substrateof the liquid crystal panel. A common electrode used commonly for thepicture elements is formed in the other substrate of the liquid crystalpanel. When voltage is applied between the picture element electrode andthe common electrode, alignment directions of liquid crystal moleculeschange depending on the voltage. As a result, this changes an amount oflight which passes the liquid crystal panel and the polarizing platesarranged respectively on the two sides of the liquid crystal panel. Ifapplied voltage were controlled for each of the picture elements, adesired image can be displayed on the liquid crystal display device.

With regard to a TN (Twisted Nematic) mode liquid crystal display devicewhich has been heretofore used widely, liquid crystal with positivedielectric anisotropy is used, and liquid crystal molecule is twistedand aligned between the two substrates. However, the TN mode liquidcrystal display device has a disadvantage of having insufficient viewingangle characteristics. In other words, with regard to the TN mode liquidcrystal display device, tone and contrast are extremely deterioratedwhen the liquid crystal panel is viewed in an oblique direction.Accordingly, the contrast is reversed in extreme cases.

An IPS (In-Plane Switching) mode liquid crystal display device and a MVA(Multi-domain Vertical Alignment) mode liquid crystal display devicehave been known as liquid crystal display devices having good viewingangle characteristics. With regard to the IPS mode liquid crystaldisplay device, picture element electrodes shaped like a line and commonelectrodes shaped like a line are arranged alternately in one of the twosubstrates. If voltage were applied between one of the picture elementelectrodes and neighboring one of the common electrodes, theorientations respectively of the liquid crystal molecules change in aplane parallel with a surface of the substrate depending on the voltage.

Although, however, the IPS mode liquid crystal display device is good atviewing angle characteristics, the orientations respectively of theliquid crystal molecules above the picture element electrode and thecommon electrode cannot be controlled since voltage is applied in adirection which is parallel with the substrate. This brings about adisadvantage that the IPS mode liquid crystal display devicesubstantially has a low aperture ratio, and that the screen of it isdark if a powerful backlight were not used.

With regard to the MVA mode liquid crystal display device, pictureelement electrodes are formed in one of the two substrates, and a commonelectrode is formed in the other of the two substrates. In addition,with regard to a generally-used MVA mode liquid crystal display device,bank-shaped protrusions made of dielectric material extending in anoblique direction are formed on the common electrode. Each of thepicture element electrodes is provided with slits parallel with theprotrusions.

With regard to the MVA mode liquid crystal display device, while voltageis not being applied, the liquid crystal molecules are aligned in adirection perpendicular to the substrates. When voltage is appliedbetween each of the picture element electrodes and the correspondingcommon electrode, the liquid crystal molecules are aligned to tilt at anangle corresponding to the voltage. In this occasion, a plurality ofdomains are formed in each of the picture elements by the slits providedinto the picture element electrode and by the corresponding bank-shapedprotrusions. The directions in which the liquid crystal molecules tiltvary from one domain to another. If the plurality of domains were formedin any one of the picture elements while the directions in which theliquid crystal molecules tilt vary from one domain to another, goodviewing angle characteristics can be obtained.

With regard to the aforementioned MVA mode liquid crystal displaydevice, the slits and the protrusions decrease the substantial apertureratio. Accordingly, the substantial aperture ratio of the MVA modeliquid crystal display device is lower than that of the TN mode liquidcrystal display device, although the substantial aperture ratio is notso low as that of the IPS mode liquid crystal display device. For thisreason, the MVA mode liquid crystal display device needs a powerfulbacklight. As a result, this kind of MVA mode liquid crystal displaydevice has hardly been adopted for a notebook personal computer, whichrequires power consumption to be low.

Japanese Patent Laid-open Official Gazette No. 2003-149647 has discloseda MVA mode liquid crystal display device which was developed in order tosolve the aforementioned problems. FIG. 1 is a plan view showing the MVAmode liquid crystal display device. Incidentally, FIG. 1 shows twopicture element regions.

A plurality of gate bus lines 11 extending in the horizontal direction(X-axis direction) and a plurality of data bus lines 12 extending in thevertical direction (Y-axis direction) are formed on one of the twosubstrates constituting a liquid crystal panel. An insulating film (gateinsulating film) is formed in each of the rectangular areas defined bythe gate bus lines 11 and the data bus lines 12. This formationelectrically isolates the gate bus lines 11 from the data bus lines 12.Each of the rectangular areas defined by the gate bus lines 11 and thedata bus lines 12 is a picture element region.

A TFT (thin film transistor) 14 and a picture element electrode 15 areformed in each of the picture element region. As shown in FIG. 1, theTFT 14 uses part of the gate bus line 11 so as to cause the part tofunction as a gate electrode. A semiconductor film (not illustrated)which functions as an active layer of the TFT 14 is formed above thegate electrode. A drain electrode 14 a and a source electrode 14 b areconnected respectively to the two sides of this semiconductor film inthe Y-axis direction. The source electrode 14 b of the TFT 14 iselectrically connected to the data bus line 12, and the drain electrode14 a is electrically connected to the picture element electrode 15.

In this patent application, out of the two electrodes connected to thesemiconductor film which functions as the active layer of the TFT, oneelectrode to be connected to the data bus line is termed as a sourceelectrode, and the other electrode to be connected to the pictureelement electrode is termed as a drain electrode.

The picture element electrode 15 is formed of a transparent conductivematerial such as ITO (Indium-Tin Oxide). Slits 15 a are formed in thispicture element electrode 15 in order to cause liquid crystal moleculesto be aligned in one of four directions when voltage is applied. Inother words, the picture element electrode 15 is divided into fourdomains with the center line in parallel with the X-axis direction andthe center line in parallel with the Y-axis direction defined asboundaries. A plurality of slits 15 a extending in a direction at anangle of 45 degrees to the X axis are formed in a first domain (upperright domain). A plurality of slits 15 a extending in a direction at anangle of 135 degrees to the X axis are formed in a second domain (upperleft domain). A plurality of slits 15 a extending in a direction at anangle of 225 degrees to the X axis are formed in a third domain (lowerleft domain). A plurality of slits 15 a extending in a direction at anangle of 315 degrees to the X axis are formed in a fourth domain (lowerright domain). A vertical alignment film (not illustrated) made ofpolyimide is formed on the picture element electrode 15.

Black matrices, color filters and a common electrode are formed in theother substrate. The black matrices are made of a metal such as Cr(chromium), or of black resin. The black matrices are arrangedrespectively in positions, each of which is opposite to any one of thegate bus lines 11, the data bus lines 12 and the TFTs 14. The colorfilters are classified into three types, such as red, green and blue.Any one of the three types of color filters is arranged in each of thepicture elements. The common electrode is made of a transparentconductive material such as ITO, and is formed on the color filters. Avertical alignment film made of polyimide is formed on the commonelectrode.

A liquid crystal panel is constituted in the following manner. Thesesubstrates are arranged to be opposite to each other with spacers (notillustrated) interposed between the two substrates. Liquid crystal withnegative dielectric anisotropy is filled between the two substrates.Hereinafter, out of the two substrates constituting the liquid crystalpanel, one substrate on which a TFT is formed will be termed as a TFTsubstrate, and the other substrate which is arranged to be opposite tothe TFT substrate will be termed as an opposing substrate.

In the case of the MVA mode liquid crystal display device shown in FIG.1, the liquid crystal molecules are aligned virtually perpendicularly tothe surface of each of the substrates while voltage is not being appliedto the picture element electrode 15. When voltage is applied to thepicture element electrode 15, the liquid crystal molecules 10 tilt inthe directions in which the respective slits 15 a extend asschematically shown in FIG. 1. Accordingly, four domains are formed inany of the picture elements while the directions in which the liquidcrystal molecules tilt vary from one domain to another. This inhibitslight from leaking in oblique directions, and thus securing good viewingangle characteristics.

Changing the subject. In the case of the MVA mode liquid crystal displaydevice shown in FIG. 1, it remains to be determined whether the liquidcrystal molecules 10 tilt inwards (in directions of the center of thepicture element) or outwards (in directions of the outside of thepicture element), immediately after voltage is applied to the pictureelement electrode 15. First of all, the electric field in extremities ofthe picture element electrode 15 determines the liquid crystal molecules10 in extremities of the slits 15 a (near the data bus line 12) to tiltinwards. Subsequently, the liquid crystal molecules 10 in positionsinwards from the extremities tilt towards the center of the pictureelement. Then, the liquid crystal molecules 10 in positions furtherinwards from the extremities tilt towards the center of the pictureelement. This process is repeated until all the liquid crystal moleculestilt towards the center of the picture element. Accordingly, it takestime for all the liquid crystal molecules 10 in a picture element tocomplete tilting in predetermined directions. This brings about aproblem that the response time is long.

The aforementioned Japanese Patent Laid-open Official Gazette No.2003-149647 has disclosed that a liquid crystal display device isfabricated in the following manner. First, liquid crystal to which apolymer component (monomer) is added is filled into the space betweenthe pair of the substrates. Then, voltage is applied between the pictureelement electrode and the common electrode, thereby causing the liquidcrystal to align in predetermined directions. Thereafter, beams ofultraviolet light are irradiated to the polymer component, and therebythe polymer component is polymerized. By this, polymer is made in theliquid crystal layer. In the case of the liquid crystal display devicethus fabricated, the polymer in the liquid crystal layer determinesdirections in which the liquid crystal molecules tilt. For this reason,no sooner is voltage applied between the picture element electrode andthe common electrode than all of the liquid crystal molecules in thepicture element start to tilt in predetermined directions. Accordingly,the response time is reduced to a large extent.

In addition, addition of a polymer component to liquid crystal has beendisclosed, also, by Japanese Patent Laid-open Official Gazette No. Hei.11-95221 and Japanese Patent Laid-open Official Gazette No. Hei.8-36186.

In general, in the case of a vertical alignment (VA) mode liquid crystaldisplay device, it has been known that the gray-scale brightnesscharacteristics to be observed when the liquid crystal display device isviewed from the front is different from that to be observed when theliquid crystal display device is viewed in an oblique direction. Theaforementioned MVA mode liquid crystal display device also has the samedefect. FIG. 2 is a diagram showing a gray-scale brightnesscharacteristics to be observed when the MVA mode liquid crystal displaydevice is viewed from the front, and a gray-scale brightnesscharacteristics to be observed when the MVA mode liquid crystal displaydevice is viewed in a direction at an azimuth angle of 90 degrees and ata polar angle of 60 degrees (in a direction downwards diagonally). InFIG. 2, the axis of abscissa represents the gray scale, and the axis ofordinate represents the transmittance. It should be noted that, in thispatent application, the center of the liquid crystal panel is defined asthe origin of ordinates, an angle between the x axis of the liquidcrystal panel and a line along which a line of sight is projected ontothe liquid crystal panel is termed as an azimuth angle, and an anglebetween a normal line of the liquid crystal panel and the line of sightis termed as a polar angle. Brightness between black and white isdivided into 256 gray scales in FIG. 2. Each gray scale corresponds toapplied voltage to a picture element electrode. The larger the grayscale number is, the larger voltage is applied to the picture elementelectrode. Furthermore, in FIG. 2, a transmittance is indicated by avalue relative to the transmittance (Twhite) which is defined as 1 (one)when white is displayed.

As understood from FIG. 2, in the case of the conventional MVA modeliquid crystal display device, the gray-scale transmittancecharacteristics to be observed when the liquid crystal display device isviewed from the front is much different from that to be observed whenthe liquid crystal display device is viewed in an oblique direction. Forthis reason, the conventional MVA mode liquid crystal display device hasa disadvantage that the display quality is deteriorated when viewed inan oblique direction although a preferable display quality can beobtained when viewed from the front. In particular, as understood fromFIG. 2, the line representing the gray-scale transmittancecharacteristics to be observed when the liquid crystal is viewed in theoblique direction undulates to a large extent in comparison with theline representing the gray-scale transmittance characteristics to beobserved when the liquid crystal display device is viewed from thefront. Accordingly, when middle gray-scales are displayed, thedifference in brightness becomes smaller between the viewing from thefront and the viewing in the oblique direction. For this reason, aphenomenon occurs in which an image to be viewed in the obliquedirection looks whitish (washes out) in comparison with that to beviewed from the front, thus deteriorating the display quality. Moreover,an anisotropy in terms of a refractive index of the liquid crystal haswavelength dependency. For this reason, color to be seen when theconventional MVA mode liquid crystal display device is viewed from thefront is much different from that to be seen when the conventional MVAmode liquid crystal display device is viewed in the oblique direction insome cases.

Furthermore, the slits 15 a of the picture element electrode 15 as shownin FIG. 1 are formed by use of a photolithography technique. Unevennessof the thickness of a photoresist film and a slight difference (shotirregularity) in exposure during stepper exposure make the widths of therespective slits 15 a ununiformed. This causes optical characteristicsof the picture element to be irregular, thus constituting a cause ofdisplay unevenness. For example, when a display is performed with middlegray scales in the entire surface of the panel, tile-shaped patternsappear in some cases.

Additionally, improvement of the substantial aperture ratio and furtherreduction in power consumption have been awaited. In addition, in thecase of a recent liquid crystal display device, further improvement inits response characteristics has been awaited.

SUMMARY OF THE INVENTION

With the aforementioned matters taken into consideration, an object ofthe present invention is to provide a MVA mode liquid crystal displaydevice whose substantial aperture ratio is higher so as to be applicableto a notebook personal computer, and which is better at the displayquality even when viewed in an oblique direction.

Another object of the present invention is to provide a MVA mode liquidcrystal display device whose substantial aperture ratio can be furtherimproved.

Yet another object of the present invention is to provide a MVA modeliquid crystal display device, whose substantial aperture ratio ishigher so as to be applicable to a notebook personal computer, whichprevents display unevenness from occurring due to a photolithographyprocess, and which accordingly is better at the display quality.

Still another object of the present invention is to provide a MVA modeliquid crystal display device whose substantial aperture ratio is higherso as to be applicable to a notebook personal computer, and which isbetter at the response characteristics.

The aforementioned problems are solved by a liquid crystal displaydevice which has the following configuration. The liquid crystal displaydevice includes: a first and a second substrates which are arranged tobe opposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. In thefirst substrate, a switching element, a first sub picture elementelectrode and a second sub picture element electrode are formed for eachpicture element. The first sub picture element electrode is constitutedof a plurality of band-shaped microelectrode parts, and a connectingelectrode part which electrically connects the microelectrode parts withone another. The second sub picture element electrode is constituted ofa plurality of band-shaped microelectrode parts, and a connectingelectrode part which electrically connects the microelectrode parts withone another. In the second substrate, a common electrode which isopposite to the first and the second sub picture element electrodes isformed. First voltage is applied to the first sub picture elementelectrode through the switching element. Second voltage which is lowerthan the first voltage is applied to the second sub picture elementelectrode.

In the case of the present invention, voltage, which is lower than thatto be applied to the first sub picture element electrode, is applied tothe second sub picture element electrode. If there were a plurality offields whose applied voltages are different from each other in a singlepicture element in the aforementioned manner, this inhibits a phenomenon(termed as “wash out”) in which the screen would otherwise look whitishwhen being viewed in an oblique direction. Accordingly, the displayquality is improved.

The aforementioned problem is solved by a liquid crystal display devicewhich has the following configuration. The liquid crystal display deviceincludes: a first and a second substrates which are arranged to beopposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. In thefirst substrate, a switching element and a picture element electrode areformed for each picture element. The picture element electrode isconstituted of a plurality of band-shaped microelectrode parts and aconnecting electrode part which electrically connects the microelectrodeparts with one another. The microelectrode part has a notch in a portionof its extremity, the portion being opposite to no neighboringmicroelectrode part.

Liquid crystal molecules between a microelectrode part and a bus lineare aligned in a direction which is different from a direction in whichthe microelectrode part extends. This causes a dark portion between themicroelectrode part and the bus line, thus constituting a cause fordecreasing the substantial aperture ratio. If the interval between themicroelectrode part and the bus line were made smaller, this makessmaller an area where the dark portion occurs, thud enabling thesubstantial aperture ratio to be improved. In this case, however, thecapacitance between the microelectrode part and the bus line becomeslarger. This deteriorates the display quality due to the crosstalk.

Meanwhile, the portion of the extremity of the microelectrode part,which portion is opposite to no neighboring microelectrode part, makesno contribution to aligning the liquid crystal molecules inpredetermined directions. In addition, the portion constitutes a causefor increasing a parasitic capacitance between the microelectrode partand the bus line. With this taken into consideration, in the case of thepresent invention, a notch is provided to the portion of the extremityof the microelectrode part, which portion is opposite to no neighboringmicroelectrode part. Thereby, the crosstalk can be inhibited fromoccurring, and the substantial aperture ratio can be improved.

The aforementioned problem is solved by a liquid crystal display devicewhich has the following configuration. The liquid crystal display deviceincludes: a first and a second substrates which are arranged to beopposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. In thefirst substrate, a switching element and a picture element electrode areformed for each picture element. The picture element electrode isconstituted of a plurality of band-shaped microelectrode parts, and aconnecting electrode part which electrically connects the microelectrodeparts with one another. A shape of an area between two neighboringmicroelectrode parts, which area is located near the base ends of thetwo neighboring microelectrode parts, is symmetrical along the centerline of the area between two neighboring microelectrode parts.

If the shape of an area between two neighboring microelectrodes, whicharea is located near the base ends of the two neighboring microelectrodeparts, were symmetrical along the center line of the area between twoneighboring microelectrode parts as described above, this enables liquidcrystal molecules in the area to be aligned in the same direction as themicroelectrode parts extend. Thereby, the dark portion is inhibited fromoccurring, and accordingly the substantial aperture ratio is improved.

The aforementioned problem is solved by a liquid crystal display devicewhich has the following configuration. The liquid crystal display deviceincludes: a first and a second substrates which are arranged to beopposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. In thefirst substrate, a switching element and a picture element electrode areformed for each picture element. The picture element electrode isconstituted of a plurality of band-shaped microelectrode parts, and aconnecting electrode part which electrically connects the microelectrodeparts with one another. The microelectrode part includes a notch in theportion of the extremity of the microelectrode part, which portion isopposite to no neighboring microelectrode part. A shape of an areabetween two neighboring microelectrode parts, which area is located nearthe base ends of the two neighboring microelectrode parts, issymmetrical along the center line of the area between two neighboringmicroelectrode parts.

In the case of the present invention, alignment disorder of the liquidcrystal molecules are inhibited in the area between two neighboringmicroelectrode parts, which area is located near the base ends of thetwo neighboring microelectrodes, and also in the area between twoneighboring microelectrode parts, which area is located near theextremities of the two neighboring microelectrode parts. Accordingly,the substantial aperture ratio can be further improved. This enables theliquid crystal display device to consume far less electric power.

The aforementioned problem is solved by a liquid crystal display devicewhich has the following configuration. The liquid crystal display deviceincludes: a first and a second substrates which are arranged to beopposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. In thefirst substrate, each picture element is provided with: a gate bus line,a data bus line, an auxiliary capacitance bus line, a switching element,a first sub picture element electrode, a second picture elementelectrode, an auxiliary capacitance electrode, control electrodes, andauxiliary capacitance lower electrodes. The gate bus line extends in adirection. The data bus line extends in a direction which crosses thegate bus line. The auxiliary capacitance bus line is in parallel withthe gate bus line. The switching element is formed in each of pictureelement regions defined by the gate bus lines and the data bus lines.The first sub picture element electrode is constituted of a plurality ofband-shaped microelectrode parts, and a connecting electrode part whichelectrically connects the microelectrode parts with one another. Thefirst sub picture element electrode includes a plurality of domaincontrol fields which are different from one another in alignmentdirection of liquid crystal molecules, and is directly connected withthe switching element. The second sub picture element electrode isarranged in the same picture element region as the first sub pictureelement electrode is, and is constituted of a plurality of band-shapedmicroelectrode parts, and a connecting electrode part which electricallyconnects the microelectrode parts with one another. The second subpicture element electrode includes a plurality of domain control fieldswhich are different from one another in alignment direction of liquidcrystal molecules. The auxiliary capacitance electrode is arranged in aposition opposite to the auxiliary capacitance bus line with a firstinsulating film interposed therebetween. The control electrodes areconnected to the switching element, and are arranged respectively in aposition opposite to a boundary between a domain control field of thefirst sub picture element electrode and a corresponding domain controlfield of the second sub picture element electrode, and in a positionopposite to a boundary between another domain control field of the firstsub picture element electrode and another corresponding domain controlfield of the second sub picture element electrode. The controlelectrodes are capacitively coupled to the corresponding second subpicture element electrodes through a second insulating film. Theauxiliary capacitance lower electrodes are connected to the auxiliarycapacitance bus line, and are arranged in positions oppositerespectively to the control electrodes with the first insulating filminterposed therebetween. In the second substrate, a common electrodewhich is opposite to the first and the second sub picture elementelectrodes is formed.

In the case of the present invention, the control electrode and theauxiliary capacitance lower electrode are arranged with the firstinsulating film interposed therebetween, in the position opposite to theboundary between a domain control field of the first sub picture elementelectrode and a corresponding domain control field of the second subpicture element electrode. This increases a capacitance value of anauxiliary capacitance connected to a picture element electrode inparallel, thus improving the response characteristics.

The aforementioned problem is solved by a liquid crystal display devicewhich has the following configuration. The liquid crystal display deviceincludes: a first and a second substrates which are arranged to beopposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. In thefirst substrate, a switching element, and a picture element electrodewhich is divided into a plurality of fields which are different from oneanother in alignment direction of liquid crystal molecules are formedfor each picture element. With regard to the picture element electrode,each of its fields is constituted of a plurality of band-shapedmicroelectrode parts, and a connecting electrode part which electricallyconnects the microelectrode parts with one another. The width of themicroelectrode part corresponding to an edge of the picture element islarger than that corresponding to a center portion of the pictureelement.

If the width of the microelectrode part corresponding to an edge of thepicture element were larger than that corresponding to a center portionof the picture element in this manner, this can avoid display unevennesswhich would otherwise occur due to a photolithography process.

The aforementioned problem is solved by a liquid crystal display devicewhich has the following configuration. The liquid crystal display deviceincludes: a first and a second substrates which are arranged to beopposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. In thefirst substrate, a switching element, a first sub picture elementelectrode and a second sub picture element electrode are formed for eachpicture element. The first sub picture element electrode is divided intoa plurality of fields which are different from one another in alignmentdirection of liquid crystal molecules. The second sub picture elementelectrode is divided into a plurality of fields which are different fromone another in alignment direction of liquid crystal molecules. Withregard to the first sub picture element electrode, each of its fields isconstituted of: a plurality of band-shaped microelectrode partsextending in a predetermined direction; and a connecting electrode partwhich electrically connects the microelectrode parts with one another.The first sub picture element electrode is directly connected to theswitching element. With regard to the second sub picture elementelectrode, each of its fields is constituted of: a plurality ofband-shaped microelectrode parts extending in a predetermined direction;and a connecting electrode part which electrically connects themicroelectrode parts with one another. The second sub picture elementelectrode is connected to the switching element through capacitivecoupling. The width of each of the microelectrode parts in the first subpicture element electrode is larger than the width of each of themicroelectrode parts in the second sub picture element electrode.

If, as described above, the width of each of the microelectrode parts inthe first sub picture element electrode directly connected to theswitching element were larger than the width of each of themicroelectrode parts in the second sub picture element electrodeconnected to the switching element through capacitive coupling, this canavoid display unevenness which would otherwise occur due to aphotolithography process.

The aforementioned problem is solved by a liquid crystal display devicewhich has the following configuration. The liquid crystal display deviceincludes: a first and a second substrates which are arranged to beopposite to each other; liquid crystal with negative dielectricanisotropy which is contained between the first and the secondsubstrates; and a polymer which is made by polymerizing a polymercomponent added to the liquid crystal, and which determines a directionin which liquid crystal molecules tilt when voltage is applied. Withregard to the first substrate, a switching element as well as a firstand a second sub picture element electrodes are formed in each of itspicture elements. The first sub picture element electrode is dividedinto a plurality of fields which are different from one another inalignment direction of liquid crystal molecules. The second sub pictureelement electrode is divided into a plurality of fields which aredifferent from one another in alignment direction of liquid crystalmolecules. With regard to the first sub picture element electrode, eachof its fields is constituted of a plurality of band-shapedmicroelectrode parts extending in a predetermined direction, and aconnecting electrode part which electrically connects the microelectrodeparts with one another. The first sub picture element electrode isdirectly connected to the switching element. With regard to the secondsub picture element electrode, each of its fields is constituted of aplurality of band-shaped microelectrode parts extending in apredetermined direction, and a connecting electrode part whichelectrically connects the microelectrode parts with one another. Thesecond sub picture element electrode is connected to the switchingelement through capacitive coupling. Ten percent to seventy percent is aratio of an area of the first sub picture element electrode to a sum ofthe area of the first sub picture element electrode and an area of thesecond sub picture element electrode.

If an area ratio of the first sub picture element electrode directlyconnected to the switching element were in a range of 10% to 70%, thiscan inhibit a phenomenon in which the screen looks whitish while viewedin an oblique direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an example of a conventional MVA modeliquid crystal display device.

FIG. 2 is a diagram showing gray-scale brightness characteristics to beobserved when the conventional MVA mode liquid crystal display device isviewed from the front and gray-scale brightness characteristics to beobserved when the conventional MVA mode liquid crystal display device isviewed in a direction at an azimuth angle of 90 degrees and at a polarangle of 60 degrees.

FIG. 3 is a plan view showing a liquid crystal display device accordingto a first embodiment of the present invention.

FIG. 4 is a cross-sectional schematic view showing the liquid crystaldisplay device according to the first embodiment.

FIG. 5 is a diagram showing transmittance-applied voltagecharacteristics to be observed when the liquid crystal display deviceaccording to the first embodiment is viewed from the front, andtransmittance-applied voltage characteristics to be observed when theliquid crystal display device according to the first embodiment isviewed in an oblique direction.

FIG. 6 is a plan view showing a liquid crystal display device accordingto a second embodiment of the present invention.

FIG. 7 is a plan view showing a liquid crystal display device accordingto a third embodiment of the present invention.

FIG. 8 is a plan view showing a liquid crystal display device accordingto a fourth embodiment of the present invention.

FIG. 9 is a plan view showing a liquid crystal display device accordingto a fifth embodiment of the present invention.

FIG. 10 is a schematic diagram showing alignment of liquid crystalmolecules in the case of an MVA mode liquid crystal display device.

FIG. 11 is a plan view, and a partially enlarged view of the plan view,both showing a liquid crystal display device according to a firstexample of a sixth embodiment of the present invention.

FIG. 12 is a plan view, and a partially enlarged view of the plan view,both showing a liquid crystal display device according to a secondexample of the sixth embodiment of the present invention.

FIG. 13 is a plan view, and a partially enlarged view of the plan view,both showing a liquid crystal display device according to a thirdexample of the sixth embodiment of the present invention.

FIG. 14 is a plan view showing a liquid crystal display device accordingto a seventh embodiment of the present invention.

FIG. 15 is a cross-sectional view taken along the I-I line in FIG. 14.

FIG. 16 is a diagram showing relationship between a capacitance ratio ofa picture element and a voltage ratio.

FIG. 17 is a diagram showing transmittance characteristics and alignmentcharacteristics in the case of the liquid crystal display deviceaccording to the seventh embodiment.

FIG. 18 is a plan view showing a liquid crystal display device accordingto an eighth embodiment of the present invention.

FIG. 19 is a diagram showing transmittance characteristics and alignmentcharacteristics in the case of the liquid crystal display deviceaccording to the eighth embodiment.

FIG. 20 is a plan view showing another example of a liquid crystaldisplay device according to the eighth embodiment.

FIG. 21 is a plan view showing a liquid crystal display device accordingto a ninth embodiment of the present invention.

FIG. 22 is a diagram showing transmittance characteristics in the caseof the liquid crystal display device according to the ninth embodiment.

FIGS. 23A and 23B are diagrams respectively showing a light transmissioncondition to be observed when voltage is applied in the case of a liquidcrystal display device (without black matrices) in which an intervalbetween a microelectrode part and a data bus line is 7 μm, and a lighttransmission condition to be observed when voltage is applied in thecase of a liquid crystal display device (without black matrices) inwhich an interval between a microelectrode part and a data bus line is 5μm.

FIGS. 24A and 24B are diagrams respectively showing a light transmissioncondition to be observed when voltage is applied in the case of a liquidcrystal display device (with black matrices) in which an intervalbetween a microelectrode part and a data bus line is 7 μm, and a lighttransmission condition to be observed when voltage is applied in thecase of a liquid crystal display device (with black matrices) in whichan interval between a microelectrode part and a data bus line is 5 μm.

FIGS. 25A and 25B are diagrams showing a result of examining transitioncharacteristics of a liquid crystal display device from a time whenvoltage is applied to the liquid crystal till a time when alignment ofthe liquid crystal becomes stable by use of a high-speed camera.

FIG. 26 is a plan view showing a liquid crystal display device accordingto a first example of a tenth embodiment.

FIG. 27 is a plan view showing a liquid crystal display device accordingto a second example of the tenth embodiment.

FIG. 28 is a plan view showing a liquid crystal display device accordingto a third example of the tenth embodiment.

FIG. 29 is a plan view showing a liquid crystal display device accordingto a fourth example of the tenth embodiment.

FIG. 30 is a diagram showing relationship among white display voltage, adirectly-connected picture element electrode ratio and an amount ofdifference in gamma values.

FIG. 31 is a plan view showing a liquid crystal display device (Part 1)according to an eleventh embodiment of the present invention.

FIG. 32 is a plan view showing the liquid crystal display device (Part2) according to the eleventh embodiment of the present invention.

FIG. 33 is a plan view showing the liquid crystal display device (Part3) according to the eleventh embodiment of the present invention.

FIG. 34 is a plan view showing the liquid crystal display device (Part4) according to the eleventh embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinbelow, descriptions will be provided for embodiments of thepresent invention with reference to the attached drawings.

First Embodiment

FIG. 3 is a plan view of a liquid crystal display device according to afirst embodiment of the present invention. FIG. 4 is a cross-sectionalschematic view of the liquid crystal display device according to thefirst embodiment. Incidentally, FIG. 3 shows two picture elementregions.

As shown in FIG. 4, a liquid crystal panel 100 is constituted of: a TFTsubstrate 110; an opposing substrate 130; and a liquid crystal layer140, made of liquid crystal with negative dielectric anisotropy, whichis contained in the space between the TFT substrate 110 and the opposingsubstrate 130. Polarizing plates 141 a and 141 b are arrangedrespectively on the two sides in the thickness direction of this liquidcrystal panel 100. The liquid crystal layer 140 includes a polymer whichhas been formed in the following process. Polymer components (monomer oroligomer) are added to the liquid crystal, and beams of ultravioletlight are irradiated to the polymer components. Thereby, the polymercomponents are polymerized into the polymer.

A plurality of gate bus lines 112 extending in the horizontal direction(X-axis direction) and a plurality of data bus lines 117 extending inthe vertical direction (Y-axis direction) are formed in the TFTsubstrate 110, as shown in FIG. 3. Each of rectangles defined by thesegate bus lines 112 and these data bus lines 117 is a picture elementregion. In addition, auxiliary capacitance bus lines 113 which arearranged respectively in parallel with the gate bus lines 112, and eachof which traverses the center of the picture element region, is formedin the TFT substrate 110. In the case of this embodiment, the absorptionaxis of one of the polarizing plates 141 a and 141 b is arranged inparallel with the gate bus line 112, and the absorption axis of theother of the polarizing plates 141 a and 141 b is arranged in parallelwith the data bus line 117.

A TFT 118, three sub picture element electrodes 121 a to 121 c, controlelectrodes 119 a and 119 c and an auxiliary capacitance electrode 119 bare formed in each of the picture element regions. The sub pictureelement electrodes 121 a to 121 c are made of a transparent conductivematerial such as ITO. Each of the sub picture element electrodes 121 ato 121 c is provided with slits 122 which regulate alignment directionsrespectively of liquid crystal molecules when voltage is applied.

Hereinbelow, detailed descriptions will be provided for the structure ofthe TFT substrate 110 and the opposing substrate 130 with reference tothe plan view of FIG. 3 and the cross-sectional schematic view of FIG.4.

The gate bus lines 112 and the auxiliary capacitance bus lines 113 areformed in a glass substrate 111 which is a base for the TFT substrate110. These gate bus lines 112 and these auxiliary capacitance bus lines113 are formed respectively of a metallic film into which, for example,Al (Aluminum) and Ti (Titanium) are laminated.

A first insulating film 114 (gate insulating film) made, for example, ofSiO₂, SiN or the like is formed over the gate bus lines 112 and theauxiliary capacitance bus lines 113. A semiconductor film 115 (forexample, an amorphous silicon film or a polysilicon film) which is anactive layer of the TFT 118 is formed in each predetermined area on thefirst insulating film 114. A channel protecting film 116 made of SiN orthe like is formed on top of the semiconductor film 115. A drainelectrode 118 a and a source electrode 118 b of the TFT 118 are formedrespectively on the two sides of the channel protecting film 116.

In addition, the data bus lines 117 connected respectively to the sourceelectrodes 118 b of the TFTs 118, the control electrodes 119 a and 119 cconnected respectively to the drain electrodes 118 a of the TFTs 118,and the auxiliary capacitance electrodes 119 b are formed on the firstinsulating film 114. As shown in FIG. 4, the auxiliary capacitanceelectrodes 119 b are formed in the respective positions opposite to theauxiliary capacitance bus lines 113 with the first insulating film 114interposed between the auxiliary capacitance electrodes 119 b and thecorresponding auxiliary capacitance bus lines 113. Each of an auxiliarycapacitance is constituted of the auxiliary capacitance bus line 113,the auxiliary capacitance electrode 119 b and the first insulating film114 which is interposed between the auxiliary capacitance bus line 113and the auxiliary capacitance electrode 119 b. The control electrodes119 a and 119 c are formed so as to be along the center line of each ofthe picture element regions, the center line being in parallel with theY axis. The auxiliary capacitance electrode 119 b is formed so as to bealong the center line of each of the picture element region, the centerline being in parallel with the X axis.

The data bus lines 117, the drain electrodes 118 a, the sourceelectrodes 118 b, the control electrodes 119 a and 119 c, and theauxiliary capacitance electrodes 119 b are formed respectively ofmetallic films into which Ti, Al and Ti are laminated.

A second insulating film 120 made, for example, of SiN is formed overthe data bus lines 117, the drain electrodes 118 a, the sourceelectrodes 118 b, the control electrodes 119 a and 119 c, and theauxiliary capacitance electrodes 119 b. Groups constituting of three subpicture element electrodes 121 a to 121 c are formed on the secondinsulating film 120. As shown in FIG. 4, each of the sub picture elementelectrodes 121 a is capacitively coupled to the corresponding controlelectrode 119 a with the second insulating film 120 interposed betweenthe sub picture element electrode 121 a and the control electrode 119 a.Each of the sub picture element electrodes 121 c is capacitively coupledto the corresponding control electrode 119 c with the second insulatingfilm 120 interposed between the sub picture element electrode 121 c andthe control electrode 119 c. In addition, each of the sub pictureelement electrodes 121 b is electrically connected to the correspondingauxiliary capacitance electrode 119 b through a corresponding one ofcontact holes 120 a which are made in the second insulating film 120.

As shown in FIG. 3, the sub picture element electrode 121 a is arrangedin an upper portion in the Y-axis direction of each of the pictureelement regions. In addition, the sub picture element electrode 121 a isdivided into the two bilaterally symmetrical fields (domain controlfields) with the center line in parallel with the Y axis defined as theboundary. In each of the picture elements, a plurality of slits 122extending in a direction at an angle of approximately 45 degrees to theX axis are formed in the right field. A plurality of slits 122 extendingin a direction at an angle of approximately 135 degrees to the X axisare formed in the left field.

The sub picture element electrode 121 b is positioned in the center ofeach of the picture element regions, and is divided into four fields(domain control fields) by the center line in parallel with the X axisand the center line in parallel with the Y axis. A plurality of slits122 extending in a direction at an angle of approximately 45 degrees tothe X axis are formed in a first field located upper right. A pluralityof slits 122 extending in a direction at an angle of approximately 135degrees to the X axis are formed in a second field located upper left. Aplurality of slits 122 extending in a direction at an angle ofapproximately 225 degrees to the X axis are formed in a third fieldlocated lower left. A plurality of slits 122 extending in a direction atan angle of approximately 315 degrees to the X axis are formed in afourth field located lower right.

The sub picture element electrode 121 c is arranged in a lower portionin the Y-axis direction of each of the picture element regions. Inaddition, the sub picture element electrode 121 c is divided into thetwo bilaterally symmetrical fields (domain control fields) with thecenter line in parallel with the Y axis defined as the boundary. Aplurality of slits 122 extending in a direction at an angle ofapproximately 225 degrees to the X axis are formed in the left field. Aplurality of slits 122 extending in a direction at an angle ofapproximately 315 degrees to the X axis are formed in the right field.The width of each of the slits 122 respectively of the sub pictureelement electrodes 121 a to 121 b is, for example, 3.5 μm. The intervalbetween each two neighboring slits (the width of a microelectrode part)is, for example, 6 μm.

It should be noted that, in the specification for this patentapplication, a conductor part, shaped like a belt, between each twoneighboring slits in each of the picture element electrodes and in eachof the sub picture element electrodes is termed as a microelectrodepart, and a part which electrically connects base ends respectively ofthe microelectrode parts is termed as a connecting electrode part.

A vertical alignment film (not illustrated) made of polyimide or thelike is formed over the sub picture element electrodes 121 a to 121 b.

On the other hand, black matrices (light blocking films) 132, colorfilters 133 and a common electrode 134 are formed in one surface (on thelower side in FIG. 4) of a glass substrate 131 which is a base of theopposing substrate 130.

The black matrices 132 are arranged respectively in positions oppositeto the gate bus lines 112, the data bus lines 117 and the TFTs 118 inthe TFT substrate 110. Color filters 133 are classified into threetypes, such as red, green and blue. A color filter with any one of thethree colors is arranged in each of the picture element regions. Onepixel is constituted of three neighboring picture elements of a redpicture element, a green picture element and a blue picture element. Thepixel is designed to be capable of displaying various colors.

The common electrode 134 is formed of a transparent conductive materialsuch as ITO, and is arranged on the color filter 133 (on the lower sideof the color filter 133 in FIG. 4). A vertical alignment film (notillustrated) made of polyimide or the like is formed on the commonelectrode 134 (on the lower side of the common electrode 134 in FIG. 4).

In the case of the liquid crystal display device thus configuredaccording to this embodiment, when a display signal is applied to thedata bus lines 117 and concurrently a predetermined voltage (scansignal) is applied to the gate bus lines 112, the TFTs 118 are turnedon. Thereby, a display signal is transmitted to the control electrodes119 a and 119 c as well as the auxiliary capacitance electrodes 119 b.With regard to each of the picture elements, since the sub pictureelement electrode 121 b is connected to the auxiliary capacitanceelectrode 119 b through the contact hole 120 a, the voltage of the subpicture element electrode 121 b is equal to the voltage of the displaysignal.

On the other hand, voltage corresponding to a capacitance value betweenthe sub picture element electrode 121 a and the control electrode 119 ais applied to the sub picture element electrode 121 a, and voltagecorresponding to a capacitance value between the sub picture elementelectrode 121 c and the control electrode 119 c is applied to the subpicture element electrode 121 c. At this point, voltage V1 to be appliedcommonly to the sub picture element electrodes 121 a and 121 c isexpressed byV1=VD·C2/(C1+C2)while the voltage of the display signal is denoted by VD; a capacitancevalue between a group of the sub picture element electrodes 121 a and121 c as well as a group of the common electrode 134 is denoted by C1;and a capacitance value between a group of the sub picture elementelectrodes 121 a and 121 c as well as a group of the control electrodes119 a and 119 c is denoted by C2.

In other words, voltage, which is lower than the voltage to be appliedto the sub picture element electrode 121 b, is applied commonly to thesub picture element electrodes 121 a and 121 c. This means that onepicture element has two types of fields which are different from eachother in transmittance-applied voltage characteristics (TVcharacteristics). In addition, the summation of thetransmittance-applied voltage characteristics respectively of the twotypes of fields represents the transmittance-applied voltagecharacteristics of the overall picture element. It has been known that,if a plurality of types of fields which are different from one anotherin transmittance-applied voltage characteristics were formed in a singlepicture element, this can avoid deterioration in quality of display tobe performed when the screen is viewed in an oblique direction.

In the case of this embodiment, the capacitance values C1 and C2 are setin a way that 1 volt is the difference between a threshold value of thetransmittance-applied voltage in the field where the sub picture elementelectrode 121 b (i.e. a sub picture element electrode connected to theTFT through no capacitive coupling: hereinafter, referred to as a“directly-connected picture element electrode”) is arranged and athreshold value of the transmittance-applied voltage commonly in thefields where the respective sub picture element electrodes 121 a and 121c (i.e. sub picture element electrodes connected to the TFT throughcapacitive coupling: hereinafter, referred to as “capacitively-coupledpicture element electrodes”) are arranged. Moreover, in the case of thisembodiment, a ratio of an area of the field where the sub pictureelement electrode 121 b (directly-connected picture element electrode)is arranged to an area of the fields where the respective sub pictureelement electrodes 121 a and 121 c (capacitively-coupled picture elementelectrodes) are arranged is set at 4:6. The capacitance values C1 and C2and the area ratio may be set as needed depending on a desiredgray-scale brightness characteristics.

FIG. 5 is a diagram showing transmittance-applied voltagecharacteristics to be observed when the liquid crystal display deviceaccording to this embodiment (an example) is viewed from the front, andtransmittance-applied voltage characteristics to be observed when thesame liquid crystal display device is viewed in an oblique direction,while the horizontal axis represents the gray-scales and the verticalaxis represents the transmittance. Incidentally, FIG. 5 additionallyshows transmittance-applied voltage characteristics to be observed whena conventional liquid crystal display device with a structure as shownin FIG. 1 is viewed in an oblique direction. As learned from FIG. 5, aline representing the transmittance-applied voltage characteristics,which is observed when the liquid crystal display device according tothis embodiment is viewed in the oblique direction, undulates less thana line representing the transmittance-applied voltage characteristicswhich is observed when the conventional liquid crystal display device asshown is viewed in the same oblique direction. It can be learned fromthis that the quality of display to be performed when the liquid crystaldisplay device according to this embodiment is viewed in the obliquedirection has been improved in comparison with the quality of display tobe performed when the conventional liquid crystal display device asshown in FIG. 1 is viewed in the same oblique direction.

No beam of light is transmitted in areas surrounding a boundary betweeneach two neighboring domains whose slits 122 extend in directions whichare different from one domain to another, or in an area along the centerline of each of the picture element regions which is in parallel withthe X axis and in an area along the center line of the picture elementregion which is in parallel with the Y axis. This is because liquidcrystal molecules in such areas are aligned in the direction in parallelwith the X axis or the direction in parallel with the Y axis (i.e. indirections, in parallel with, or orthogonal to, the absorption axesrespectively of the polarizing plates 141 a and 141 b) when voltage isapplied. In the case of this embodiment, it is these boundary areas, butnot other areas, where the control electrodes 119 a and 119 c and theauxiliary capacitance electrode 119 b are provided with regard to eachof the picture elements. For this reason, reduction in the apertureratio can be minimized, although provision of the control electrodes 119a and 119 c as well as the auxiliary capacitance electrode 119 b to eachof the picture elements inevitably reduces the aperture ratio.

Hereinbelow, descriptions will be provided for a method of manufacturingthe liquid crystal display device according to this embodiment.

To begin with, the glass substrate 111 which is used as the base of theTFT substrate 110 is prepared. Subsequently, the metallic film intowhich, for example, Al (Aluminum) and Ti (Titanium) are laminated isformed on this glass substrate 111. Thereafter, the metallic film ispatterned by use of a photolithography process. Thus, the gate bus lines112 and the auxiliary bus lines 113 are formed. In this occasion, forexample, the gate bus lines 112 are formed with a pitch of approximately300 μm in the vertical direction.

Then, the first insulating film (gate insulating film) 114 made, forexample, of an insulating material such as SiO₂, SiN or the like isformed in the entire upper surface of the glass substrate 111. Thence,the semiconductor films (amorphous silicon films or polysilicon films)115 which are used respectively as the active layers of the TFTs 118 areformed in predetermined positions on the first insulating film 114.

Subsequently, the SiN film is formed in the entire upper surface of theglass substrate 111. Thereafter, the SiN film is patterned by use of aphotolithography process. Thereby, the channel protecting films 116 areformed respectively on top of areas which are used respectively as thechannels of the semiconductor film 115.

Then, an ohmic contact layer (not illustrated) made of a semiconductorfilm which has been treated with impurities in high concentration isformed in the entire upper surface of the glass substrate 111. Thence,the metallic film into which, for example, Ti, Al and Ti are laminatedin this order is formed on the glass substrate 111. Thereafter, thismetallic film and the ohmic contact layer are patterned by use of aphotolithography process. Thus, the data bus lines 117, the drainelectrodes 118 a, the source electrodes 118 b, the control electrodes119 a and 119 c, and the auxiliary capacitance electrodes 119 b areformed. In this occasion, for example, the data bus lines 117 are formedwith a pitch of approximately 100 μm in the horizontal direction.

The second insulating film 120 made of an insulating material such asSiO₂, SiN or the like is formed in the entire upper surface of the glasssubstrate 111. Then, the contact holes 120 a which respectively reachthe auxiliary capacitance electrodes 119 b are formed in the secondinsulating film 120.

Then, the entire upper surface of the glass substrate 111 is sputteredwith ITO. Thereby, the ITO film is formed. This ITO film is electricallyconnected with the auxiliary capacitance electrodes 119 b through thecontact holes 120 a. Thereafter, the ITO film is patterned by use of aphotolithography process. Thereby, the sub picture element electrodes121 a to 121 c are formed. The slits 122 extending in oblique directionsare formed in each of the sub picture element electrodes 121 a to 121 c,as described above.

Thence, the entire upper surface of the glass substrate 111 is coatedwith polyimide. Thereby, the alignment film is formed. Accordingly, theTFT substrate 110 is completed.

Next, descriptions will be provided for a method of fabricating theopposing substrate 130.

To begin with, the glass substrate 131 which is used as the base of theopposing substrate 130 is prepared. Subsequently, the black matrices 132are formed of Cr (Chromium) or black resin on the predetermined areas ofthe glass substrate 131. The black matrices 132 are formed, for example,in the respective positions opposite to the gate bus lines 112 and thedata bus lines 117 in the TFT substrate 110.

Then, red color filters, green color filters and blue color filters 133are formed on the glass substrate 131 respectively by use of redphotosensitive resin, green photosensitive resin and blue photosensitiveresin.

Thence, the entire upper surface of the glass substrate 131 is sputteredwith ITO. Thereby, the common electrode 134 is formed. Thereafter, thecommon electrode 134 is coated with polyimide. By this, the alignmentfilm is formed on the common electrode 134. Accordingly, the opposingsubstrate 130 is completed.

The TFT substrate 110 and the opposing substrate 130, which have beenthus fabricated, are arranged to be opposite to each other. Thereafter,liquid crystal with negative dielectric anisotropy is filled into thespace between the TFT substrate 110 and the opposing substrate 130. Theliquid crystal panel 100 is manufactured in this manner. A polymercomponent, for example, a polymer component (diacrylate, methacrylate orthe like) with a photo-functional group, is beforehand added to theliquid crystal by 0.3 wt %. In addition, the interval (cell gap) betweenthe TFT substrate 110 and the opposing substrate 130 is, for example,3.5 μm to 4 μm.

Subsequently, a predetermined signal is applied to the gate bus lines112, and thereby the TFT 118 of each of the picture elements is turnedinto an “on” state. In addition, a predetermined voltage is applied tothe data bus lines 117. Thereby, voltage is applied between the commonelectrode 134 and each of the sub picture element electrodes 121 a to121 c. Accordingly, the liquid crystal molecules in each of the pictureelements are aligned in predetermined directions. After the alignment ofthe liquid crystal molecules becomes sufficiently stable, beams ofultraviolet light are irradiated to the polymer component. Thereby,monomer in the liquid crystal layer is polymerized. The polymer thusmade in the liquid crystal layer determines directions in which therespective liquid crystal molecules tilt when voltage is applied.

Thereafter, the polarizing plates 141 a and 141 b are arranged on thetwo sides of the liquid crystal panel 100 in the thickness direction. Inaddition, drive circuits and backlights are installed therein. In thismanner, the liquid crystal display device according to this embodimentis completed.

Second Embodiment

FIG. 6 is a plan view showing a liquid crystal display device accordingto a second embodiment of the present invention. Incidentally, ifcomponents and equivalents in FIG. 6 were the same as, or similar to,those in FIG. 3, the components and equivalents in FIG. 6 are denoted bythe same reference numerals and symbols as those in FIG. 3 are. Thus,detailed descriptions will be omitted for the same, or similarcomponents and equivalents in FIG. 6.

In the case of this embodiment, two sub picture element electrodes 152 aand 152 b are formed in a single picture element region. The sub pictureelement electrodes 152 a (directly-connected picture element electrode)is arranged in a range upper in the Y axis direction in each of thepicture element regions. The sub picture element electrode 152 a isdivided into four fields (domain control fields) by the center line inparallel with the X axis and the center line in parallel with the Yaxis. A plurality of slits 153 extending in a direction at an angle ofapproximately 45 degrees to the X axis are formed in a first fieldlocated upper right. A plurality of slits 153 extending in a directionat an angle of approximately 135 degrees to the X axis are formed in asecond field located upper left. A plurality of slits 153 extending in adirection at an angle of approximately 225 degrees to the X axis areformed in a third field located lower left. A plurality of slits 153extending in a direction at an angle of approximately 315 degrees to theX axis are formed in a fourth field located lower right.

The sub picture element 152 b (capacitively-coupled picture elementelectrode) is arranged in a range lower in the Y axis direction in eachof the picture element regions. The area of the sub picture elementelectrode 152 b is larger than that of the sub picture element electrode152 a. Like the sub picture element electrode 152 a, the sub pictureelement electrode 152 b is divided into four fields (domain controlfields) by the center line in parallel with the X axis and the centerline in parallel with the Y axis. A plurality of slits 153 extending ina direction at an angle of approximately 45 degrees to the X axis areformed in a first field located upper right. A plurality of slits 153extending in a direction at an angle of approximately 135 degrees to theX axis are formed in a second field located upper left. A plurality ofslits 153 extending in a direction at an angle of approximately 225degrees to the X axis are formed in a third field located lower left. Aplurality of slits 153 extending in a direction at an angle ofapproximately 315 degrees to the X axis are formed in a fourth fieldlocated lower right.

Underneath the sub picture element electrodes 152 a and 152 b, a controlelectrode 151 a extending along a center line of each of the pictureelement regions is formed, the center line being in parallel with the Yaxis. This control electrode 151 a is electrically connected with thedrain electrode 118 a of each of the TFTs 118.

In addition, underneath each of the sub picture element electrodes 152a, an auxiliary capacitance bus line 113 and an auxiliary capacitanceelectrode 151 b are formed along a center line of the sub pictureelement electrode 152 a, the center line being in parallel with the Xaxis. The auxiliary capacitance bus line 113 is formed in the same layeras a gate bus line 112 is. In addition, the auxiliary capacitanceelectrode 151 b is formed in the same layer as the control electrode 151a is, and is connected with the control electrode 151 a. A firstinsulating film (an equivalent to the insulating film 114 in FIG. 4) isformed between the auxiliary capacitance bus line 113 and the auxiliarycapacitance electrode 151 b. An auxiliary capacitance is constituted ofthe first insulating film, the auxiliary capacitance bus line 113 andthe auxiliary capacitance electrode 151 b. Furthermore, the auxiliarycapacitance electrode 151 b is electrically connected with the subpicture element electrode 152 a through a contact hole 154, which hasbeen formed in a second insulating film (an equivalent to the insulatingfilm 120 in FIG. 4).

Moreover, underneath each of the sub picture element electrodes 152 b, acontrol electrode 151 c is formed along a center line of the sub pictureelement electrode 152 b, the center line being in parallel with the Xaxis. The control electrode 151 c is formed in the same layer as thecontrol electrode 151 a is, and is electrically connected with thecontrol electrode 151 a. Additionally, the control electrode 151 c iscapacitively coupled to the sub picture element electrode 152 b throughthe second insulating film.

The structure of an opposing substrate according to the secondembodiment is basically the same as that according to the firstembodiment, and descriptions will be omitted for the structure accordingto the second embodiment here. In addition, in the second embodiment,too, a polymer component such as diacrylate is added to liquid crystal,and the liquid crystal is filled into the space between a TFT substrateand the opposing substrate. Voltage is applied between a picture elementelectrode (each of the sub picture element electrodes 152 a and 152 b)and a common electrode. Thereby, liquid crystal molecules are aligned inpredetermined directions. Thereafter, beams of ultraviolet light areirradiated to the polymer component. Accordingly, the polymer componentis polymerized. Thus, a polymer is formed in the liquid crystal layer.

In the case of this embodiment, a single picture element is providedwith two types of fields which are different from each other intransmittance-applied voltage characteristics in common with the firstembodiment. This brings about an effect of avoiding deterioration in thedisplay quality to be obtained when the screen is viewed in an obliquedirection.

In addition, in the case of this embodiment, the auxiliary capacitancebus line 113 and the auxiliary capacitance electrode 151 b are formedalong the center line of the sub picture element electrode 152 a, thecenter line being in parallel with the X axis. This portion constitutesa boundary between the two domains. Accordingly, when voltage isapplied, the liquid crystal molecules tilt in a direction in parallelwith the X axis. For this reason, light is not transmitted in thisportion, even if neither the auxiliary capacitance bus line 113 nor theauxiliary capacitance electrode 151 b were provided. This can avoiddeterioration in the transmittance, which deterioration would otherwisebe caused due to formation of the auxiliary capacitance bus line 113 andthe auxiliary capacitance electrode 151 b in each of the pictureelements. Additionally, in this embodiment, if the length and the widthof the auxiliary capacitance electrode 151 b were adjusted, thecapacitance value of the auxiliary capacitance can be controlled. Thisbrings about an advantage of giving higher degree of freedom indesigning the capacitance value of the auxiliary capacitance.

In common with the auxiliary capacitance bus line 113 and the auxiliarycapacitance electrode 151 b, the control electrode 151 c is formed alongthe center line of the sub picture element electrode 152 b, the centerline being in parallel with the X axis. This can avoid deterioration inthe transmittance, which would otherwise be caused due to formation ofthe control electrode 151 c in each of the picture elements. Moreover,if the length and the width of the control electrode 151 c wereadjusted, this can control the capacitance value of connection betweenthe control electrode 151 a and the sub picture element electrode 152 band the capacitance value of connection between the control electrode151 c and the sub picture element electrode 152 b. This brings about anadvantage of giving higher degree of freedom in designing thecapacitance values of the respective connections

Third Embodiment

FIG. 7 is a plan view showing a liquid crystal display device accordingto a third embodiment of the present invention. If components andequivalents in FIG. 7 were the same as, or similar to, those in FIG. 3,the components and equivalents in FIG. 7 are denoted by the samereference numerals and symbols as those in FIG. 3 are. Thus, detaileddescriptions will be omitted for the same, or similar, components andequivalents in FIG. 7.

In the case of this embodiment, too, two sub picture element electrodes162 a and 162 b are formed in a single picture element region. The subpicture element electrode 162 a (directly-connected picture elementelectrode) is arranged in a range upper in the Y axis direction in eachof the picture element regions. The sub picture element electrode 162 ais divided into four fields (domain control fields) by the center linein parallel with the X axis and the center line in parallel with the Yaxis. A plurality of slits 163 extending in a direction at an angle ofapproximately 45 degrees to the X axis are formed in a first fieldlocated upper right. A plurality of slits 163 extending in a directionat an angle of approximately 135 degrees to the X axis are formed in asecond field located upper left. A plurality of slits 163 extending in adirection at an angle of approximately 225 degrees to the X axis areformed in a third field located lower left. A plurality of slits 163extending in a direction at an angle of approximately 315 degrees to theX axis are formed in a fourth field located lower right.

The sub picture element 162 b (capacitively-coupled picture elementelectrode) is arranged in a range lower in the Y axis direction in eachof the picture element regions. The area of the sub picture elementelectrode 162 b is larger than that of the sub picture element electrode162 a. Like the sub picture element electrode 162 a, the sub pictureelement electrode 162 b is divided into four fields (domain controlfields) by the center line in parallel with the X axis and the centerline in parallel with the Y axis. A plurality of slits 163 extending ina direction at an angle of approximately 315 degrees to the X axis areformed in a first field located upper right. A plurality of slits 163extending in a direction at an angle of approximately 225 degrees to theX axis are formed in a second field located upper left. A plurality ofslits 163 extending in a direction at an angle of approximately 135degrees to the X axis are formed in a third field located lower left. Aplurality of slits 163 extending in a direction at an angle ofapproximately 45 degrees to the X axis are formed in a fourth fieldlocated lower right.

Underneath the sub picture element electrodes 162 a and 162 b, a controlelectrode 161 a is formed along a center line of each of the pictureelements, the center line being in parallel with the Y axis. Thiscontrol electrode 161 a is electrically connected with the drainelectrode 118 a of each of the TFTs 118.

In addition, underneath each of the sub picture element electrodes 162a, an auxiliary capacitance bus line 113 and an auxiliary capacitanceelectrode 161 b are formed along a center line of the sub pictureelement electrode 162 a, the center line being in parallel with the Xaxis. The auxiliary capacitance bus line 113 is formed in the same layeras a gate bus line 112 is. In addition, the auxiliary capacitanceelectrode 161 b is formed in the same layer as the control electrode 161a is, and is electrically connected with the control electrode 161 a. Afirst insulating film (an equivalent to the insulating film 114 in FIG.4) is formed between the auxiliary capacitance bus line 113 and theauxiliary capacitance electrode 161 b. An auxiliary capacitance isconstituted of the auxiliary capacitance bus line 113, the auxiliarycapacitance electrode 161 b and the first insulating film therebetween.Furthermore, the auxiliary capacitance electrode 161 b is electricallyconnected with the sub picture element electrode 162 a through a contacthole 164, which has been formed in a second insulating film (anequivalent to the insulating film 120 in FIG. 4).

Moreover, underneath the extremity of each of the sub picture elementelectrodes 162 b, a control electrode 161 c is formed. This controlelectrode 161 c also is formed in the same layer as the controlelectrode 161 a is, and is electrically connected with the controlelectrode 161 a. The control electrode 161 c is capacitively coupled tothe sub picture element electrode 162 b through the second insulatingfilm.

The structure of an opposing substrate according to this embodiment isalso basically the same as that according to the first embodiment, anddescriptions will be omitted for the structure according to thisembodiment here. In addition, in the case of this embodiment, too, apolymer component such as diacrylate is added to liquid crystal, and theliquid crystal is filled into the space between a TFT substrate and theopposing substrate. Voltage is applied between a picture elementelectrode (each of the sub picture element electrodes 162 a and 162 b)and a common electrode. Thereby, liquid crystal molecules are aligned inpredetermined directions. Thereafter, beams of ultraviolet light areirradiated to the polymer component. Accordingly, the polymer componentis polymerized.

In the case of the second embodiment (see FIG. 6) which has beendescribed, the liquid crystal molecules between the sub picture elementelectrodes 152 a and 152 b tilt in the direction in parallel with the Xaxis when voltage is applied. This causes a dark line between the subpicture element electrodes 152 a and 152 b. By contrast, in the case ofthis embodiment, the gap between the two sub picture element electrodes162 a and 162 b extends in the same direction as the slits 163 adjacentto the gap do. This causes the liquid crystal molecules between the subpicture element electrodes 162 a and 162 b to tilt in the same directionas the slits 163 extend, when voltage is applied. Accordingly, a darkline does not appear between the sub picture element electrodes 162 aand 162 b. Thus, the substantial aperture ratio is improved.

Furthermore, in the case of this embodiment, too, a single pictureelement is provided with two types of fields which are different intransmittance-applied voltage characteristics, in common with the caseof the first embodiment. This brings about an effect of avoidingdeterioration in the display quality which would otherwise be causedwhen the screen is viewed in an oblique direction.

Fourth Embodiment

FIG. 8 is a plan view showing a liquid crystal display device accordingto a fourth embodiment of the present invention.

In the case of this embodiment, as shown in FIG. 8, each data bus line177 is formed so as to be shaped like a zigzag, which causes an upperhalf of the data bus line in each picture element to extend in adirection at an angle of 45 degrees to the X axis, and a lower half ofthe data bus line in the picture element to extend in a direction at anangle of 315 degrees to the X axis. However, each gate bus line 122 isformed so as to be in parallel with the X axis, in common with the firstto the third embodiments.

Three sub picture element electrodes 172 a, 172 b and 172 c as well as aTFT 118 are formed in each of the picture element regions to be definedby the gate bus lines 122 and the data bus lines 177. In the case ofthis embodiment, too, a part of the gate bus line 122 is used as a gateelectrode for a TFT 118. A drain electrode 118 b and a source electrode118 a are formed so as to be opposite to each other with the gate busline 122 interposed therebetween. In each of the picture elementregions, a control electrode 171 bent along the center line of thepicture element region is formed underneath the sub picture elementelectrodes 172 a to 172 c. This control electrode 171 is formed on afirst insulating film (an equivalent to the insulating film 114 in FIG.3), and is electrically connected with the drain electrode 118 b of theTFT 118.

The sub picture element electrode 172 a (a capacitively-coupled pictureelement electrode) is divided into two fields (domain control fields) bythe center line. In addition, the right field is provided with slits 173extending in a direction at an angle of approximately 315 degrees to theX axis. The left field is provided with slits 173 extending in adirection at an angle of approximately 135 degrees.

The sub picture element electrode 172 b (a directly-connected pictureelement electrode) is arranged in a center portion where each of thepicture elements is bent. The sub picture element electrode 172 b isdivided into four fields. Slits 173 extending in a direction at an angleof approximately 45 degrees to the X axis are formed in a first field.Slits 173 extending in a direction at an angle of approximately 135degrees to the X axis are formed in a second field. Slits 173 extendingin a direction at an angle of approximately 225 degrees to the X axisare formed in a third field. Slits 173 extending in a direction at anangle of approximately 315 degrees to the X axis are formed in a fourthfield. This sub picture element electrode 172 b is electricallyconnected with the control electrode 171 through a contact hole 174which is provided into a second insulating film (an equivalent to theinsulating film 120 in FIG. 3).

The sub picture element electrode 172 c (a capacitively-coupled pictureelement electrode) is divided into two fields (domain control fields) bythe center line. In addition, the right field is provided with slits 173extending in a direction at an angle of approximately 45 degrees to theX axis. The left field is provided with slits 173 extending in adirection at an angle of approximately 225 degrees. Each of the subpicture element electrodes 172 a and 172 c is connected with the controlelectrode 171 through the second insulating film.

The structure of an opposing substrate according to this embodiment isalso basically the same as that according to the first embodiment, anddescriptions will be omitted for the structure according to thisembodiment here. In the case of this embodiment, too, a polymercomponent such as diacrylate is added to liquid crystal, and the liquidcrystal is filled into the space between a TFT substrate and theopposing substrate. Voltage is applied between a picture elementelectrode (each of the sub picture element electrodes 172 a to 172 c)and a common electrode. Thereby, liquid crystal molecules are aligned inpredetermined directions. Thereafter, beams of ultraviolet light areirradiated to the polymer component. Accordingly, the polymer componentis polymerized.

In the cases of the first to the third embodiments, slits of each of thesub picture element electrodes extend in directions respectively atangles of 45 degrees, 135 degrees, 225 degrees and 315 degrees to the Xaxis. Accordingly, the liquid crystal molecules tilt in the samedirections as the slits extend. However, a line of electric force occursoutwards in the extremity of each of the sub picture element electrodes.This causes the liquid crystal molecules between each of the sub pictureelement electrodes and the data bus line to tilt in a direction inparallel with the X axis. On the other hand, with regard to one of twopolarizing plates, between which the liquid crystal panel is interposed,its absorption axis is arranged in parallel with the X axis. With regardto the other of the two polarizing plates, its absorption axis isarranged in parallel with the Y axis. In this case, dark parts occurbetween each of the sub picture element electrodes and the data bus linein each of the picture elements in the liquid crystal display deviceaccording to any one of the first to the third embodiments. This reducesthe substantial aperture ratio.

With this taken into consideration, in the case of this embodiment, thedata bus line 177 is beforehand designed to extend in directions atangles of 45 degrees and 315 degrees to the gate bus line 122 in each ofthe picture elements, as shown in FIG. 8. This causes the liquid crystalmolecules between the data bus line 177 and each of the sub pictureelement electrodes 172 a to 172 c to tilt in a direction at an angle of45 degrees to the polarization axes of the polarizing plates. Thisprevents dark parts from occurring between the data bus line 177 andeach of the sub picture element electrodes 172 a to 172 c. Thesubstantial aperture ratio is improved in the case of this embodiment incomparison with the cases of the first to the third embodiments. Thisbrings about an effect that enables further brighter display. When thetransmittance of a liquid crystal display device according to thisembodiment which had been actually manufactured was examined, it wasproved that the transmittance was improved by approximately 5% incomparison with the liquid crystal display device with a structure asshown in FIG. 3.

In the case of the liquid crystal display device according to thisembodiment, a single picture element is provided with the plurality oftypes of fields which are different from one another intransmittance-applied voltage characteristics. This brings about aneffect of improving the display quality to be observed when the screenis viewed in an oblique direction.

Fifth Embodiment

FIG. 9 is a plan view showing a liquid crystal display device accordingto a fifth embodiment of the present invention. This embodiment isdifferent from the fourth embodiment in that the shapes of the subpicture element electrodes according to this embodiment are differentfrom those of the sub picture element electrodes according to the fourthembodiment. Except for the shapes, however, this embodiment has the sameconfiguration as that according to the fourth embodiment does. Ifcomponents and equivalents in FIG. 9 were the same as, or similar to,those in FIG. 8, the components and equivalents in FIG. 9 are denoted bythe same reference numerals and symbols as those in FIG. 8 are. Thus,detailed descriptions will be omitted for the same, or similar,components and equivalents in FIG. 9.

In the case of the liquid crystal display device according to the fourthembodiment as shown in FIG. 8, many slits 173 are provided into each ofthe sub picture element electrodes 172 a to 172 c. These slits 173 areformed by use of a photolithography process. In other words, an ITOfilm, which is made into each of the sub picture element electrodes 172a to 172 c, is coated with photoresist. Thereafter, a stepper exposureprocess is performed on the ITO film, and then a development process isperformed on the ITO film. Using remaining photoresist as a mask, theITO film is etched. In this manner, the slits 173 are formed. However,each of the slits 173 is minute. This causes the widths of therespective slits to be nonuniform due to unevenness of the filmthickness of the photoresist film and due to a slight difference (shotunevenness) in amount of being exposed during the stepper exposureprocess. It is likely that this affects the optical characteristics, andthat the display quality is reduced accordingly.

With this taken into consideration, in the case of the fifth embodiment,slits 173 are formed only in extremities respectively of sub pictureelement electrodes 182 a and 182 c (corresponding to the sub pictureelement electrodes 172 a and 172 b according to the fourth embodiment)and in the bending portion of the sub picture element electrode 182 b(corresponding to the sub picture element electrode 172 b). In the caseof the liquid crystal display device according to this embodiment, whena polymer component (a monomer) added to the liquid crystal ispolymerized, it takes longer for the liquid crystal molecules tocomplete tilting in the predetermined directions after voltage isapplied, in comparison with the liquid crystal display device accordingto the fourth embodiment. However, while the liquid crystal displaydevice according to this embodiment is being in actual use, thedirections in which the liquid crystal molecules are aligned aredetermined by the polymer included in the liquid crystal layer. For thisreason, the liquid crystal display device according to this embodimentcan obtain response characteristics equal to those of the liquid crystaldisplay device according to the fourth embodiment.

Sixth Embodiment

Hereinbelow, descriptions will be provided for a sixth embodiment of thepresent invention.

In the case of the liquid crystal display device as shown in FIG. 1, thewidths respectively of the slits are caused to be nonuniform due to aphotolithography process, as described above. Accordingly, in somecases, patterns shaped like a tile are seen when a display is performedin middle gray-scale. The applicants of the present invention havecarried out various experiments and studies in order to solve such aproblem. As a result of them, the applicants have found that the displayunevenness due to the photolithography process can be prevented fromoccurring if values denoted by d, L and S are set in a way that theysatisfy an equation in the formL+d−S≧4 μm  (1)where d denotes a thickness (a cell gap) of the liquid crystal layer; L,a width of conductive material portion (i.e. a microelectrode part)between two neighboring slits; and S, a width of the slit.

For example, the thickness d of the liquid crystal layer may be 4 μm,concurrently the width L of the microelectrode part may be 6 μm, andsimultaneously the width S of the slit may be 3.5 μm.

When a liquid crystal display device was actually manufactured with theaforementioned conditions, it was proved that tile-shaped patterns whichwould otherwise occur were able to be prevented. However, a new problemoccurred which reduced brightness while a white display was beingperformed. It is conceivable that this problem came from the followingreasons.

When voltage is applied between a picture element electrode and a commonelectrode, the liquid crystal molecules (liquid crystal molecules withnegative dielectric anisotropy) tend to tilt in a direction orthogonalto a line of electric force stemming from the picture element electrode.As shown in FIG. 10, no sooner is voltage applied than the liquidcrystal molecules 203 around the extremities (near a data bus line 202)respectively of microelectrode parts 201 tilt towards the center of eachof the picture elements. Over each slits 204 and each microelectrodepart 201, the respective liquid crystal molecules 203, which are goingto tilt in directions which are opposite to each other, collide with oneanother. Eventually, these liquid crystal molecules 203 tilt in the samedirection as the slits 204 extend, under an influence of the liquidcrystal molecule 203 around the extremities respectively of themicroelectrode parts 201.

However, liquid crystal molecules 203 between the data bus line 202 andeach of the extremities of the respective microelectrode parts 201 tiltin a direction approximately perpendicular to the data bus line 202 whenvoltage is applied. This causes dark parts in this portion. If thewidths respectively of the microelectrode parts 201 are made larger (forexample, set at 6 μm), this increases a dark area, and accordinglyreducing the brightness.

It is conceivable that, for the purpose of making the dark area smaller,each of the microelectrode parts 201 are stretched so that the intervalbetween the microelectrode part 201 and the data bus line 202 is madenarrower. However, mere reduction in the interval between themicroelectrode part 201 and the data bus line 202 would result inincreasing a parasitic capacitance between the microelectrode part 201and the data bus line 202, thus causing a crosstalk. This leads todeterioration in the display quality. In other words, improvement in thebrightness and check of the crosstalk are in a tradeoff relationship.

The applicants of the present invention closely observed the alignmentstate of the liquid crystal molecules in the liquid crystal displaydevice including the picture element electrode with the shape as shownin FIG. 10. As a result of this observation, it was found that theliquid crystal molecules 203 tilt in a direction approximatelyperpendicular to the data bus line 202 in a part in the extremity ofeach of the microelectrode parts 201 (a part indicated by referencesymbol A in FIG. 10) which has no portion opposite to its neighboringmicroelectrode part 201. The extremity of each of the microelectrodeparts 201 is a factor in increasing the parasitic capacitance due to itsvicinity to the data bus line 202.

With this taken into consideration, in the case of this embodiment, aninterval between the data bus line 212 and each of the microelectrodeparts 215 b is made narrower, and concurrently a notch is provided in apart which constitutes the extremity of each of the microelectrode parts215 b, and which does not make a contribution to aligning the liquidcrystal molecules in the same direction as each of the slits 215 aextends, as shown in FIG. 11. In other words, a notch is provided in apart of the microelectrode part (a part encompassed by a circle in FIG.11) which has no portion opposite to its neighboring microelectrodepart. This avoids increasing the parasitic capacitance. This can improvethe transmittance to be observed while a white display is beingperformed, and can save the power consumption. In addition, this avoidsdeteriorating the display quality.

It should be noted that reference numeral 211 denotes a gate bus line;212, the data bus line; 214, a TFT; and 215, a picture elementelectrode. In addition, a dot-dashed line in the enlarged view of FIG.11 denotes positions respectively of the extremities of themicroelectrode parts of the conventional MVA mode liquid crystal displaydevice.

It is very difficult to form microelectrode parts, in which extremitieshave an acute angle, by use of a photolithography process. Usually, theextremities respectively of the microelectrode parts are round. Inaddition, the roundness varies from one extremity to another due to aslight change in a condition under which a photolithography process isperformed. This is a cause for making the optical characteristicsnonuniform. For this reason, it is preferable that the extremitiesrespectively of the microelectrode parts be shaped like an arc with apredetermined curvature, or like a polygon, when it is designed.

The applicants of the present invention further closely observed thealignment state of the liquid crystal molecules in the liquid crystaldisplay device whose picture element electrodes have the shape as shownin FIG. 10. As a result of this observation, it was found that theliquid crystal molecules 203 did not tilt in a direction at an angle of45 degrees in the vicinity of the base end of each of the slits 204 (apart indicated by reference symbol B in FIG. 10), and that this was acause for decreasing a degree of white brightness. It is conceivablethat this stemmed from the following reason.

The stem part of each of the picture element electrode (a partconnecting the microelectrode parts with one another: in other words, aconnection electrode 205) is formed so as to be in parallel with thegate bus line 202. With regard to liquid crystal molecules 203 in anarea B surrounded by this connection electrode 205 and themicroelectrode part 201, some of the liquid crystal molecules 203 aregoing to tilt in a direction orthogonal to a line of electric forcestemming from the connection electrode 205, and the others are going totilt in a direction orthogonal to a line of electric force stemming fromthe microelectrode part 201. As a result, the two groups of the liquidcrystal molecules 203 collide with each other. Eventually, the twogroups tilt in a direction which keeps a balance between the two groups,or in a direction of a line which bisects an angle between theconnection electrode 205 and the microelectrode part 201. This directiondeviates from the direction in which each of the slits 204 extends. Thisdecreases the transmittance while a white display is being performed.

With this taken into consideration, in the case of this embodiment, thebase end of each of the slits is designed to have a shape which issymmetrical along the center line of the slit. Specifically, forexample, as shown in FIG. 12, the base end of each of the slits 215 a isdesigned to have a shape in which the two angles at the bottom of thebase end are 90 degrees. Otherwise, for example, as shown in FIG. 13,the base end is designed to be shaped like an isosceles triangle. Theseshapes cause the liquid crystal molecules 203 around the base end ofeach of the slits 215 a to tilt in the same direction as the center lineof the slit 215 a extends. This improves the brightness.

Hereinbelow, descriptions will be provided for a result of examiningcharacteristics respectively of the liquid crystal display devicesaccording to examples of this embodiment which have been actuallymanufactured while comparing with comparative examples. It should benoted that, each of the liquid crystal display devices respectivelyaccording to the examples and the comparative examples has an opposingsubstrate with the same structure as that of the opposing substrate ofthe liquid crystal display device according to the first embodiment. Inaddition, diacrylate is added to the liquid crystal (liquid crystal withnegative dielectric anisotropy). This liquid crystal is filled in thespace between the TFT substrate and the opposing substrate. Thereafter,beams of ultraviolet light are irradiated to the diacrylate whilepredetermined voltage is being applied between the picture elementelectrode and the common electrode. A polymer is formed in the liquidcrystal layer in this manner. In addition, polarizing plates arearranged respectively on the two sides of the liquid crystal panel.

First Comparative Example

A liquid crystal display device having picture element electrodes asshown in FIG. 1 was manufactured. In the case of the liquid crystaldisplay device according to the first comparative example, the thicknessd of the liquid crystal layer was 3.8 μm, the width L of each of themicroelectrode parts was 3 μm, and the width S of each of the slits was3.5 μm. In this occasion, L+d−S took on 3.3 μm, and did not satisfy theequation (1). When a display was performed with middle gray-scale on theentire surface of the liquid crystal display device according to thefirst comparative example, tile-shaped patterns were observed.

Second Comparative Example

A liquid crystal display device having picture element electrodes asshown in FIG. 1 was manufactured. In the case of the liquid crystaldisplay device according to the second comparative example, thethickness d of the liquid crystal layer was 4 μm, the width L of each ofthe microelectrode parts was 3 μm, and the width S of each of the slitswas 3.5 μm. In this occasion, L+d−S took on 3.5 μm, and did not satisfythe equation (1). When a display was performed with middle gray-scale onthe entire surface of the liquid crystal display device according to thesecond comparative example, tile-shaped patterns were observed.

Third Comparative Example

A liquid crystal display device having picture element electrodes asshown in FIG. 1 was manufactured. In the case of the liquid crystaldisplay device according to the third comparative example, the thicknessd of the liquid crystal layer was 4 μm, the width L of each of themicroelectrode parts was 6 μm, and the width S of each of the slits was3.5 μm. In this occasion, L+d−S took on 6.5 μm, and satisfied theequation (1). When a display was performed with middle gray-scale on theentire surface of the liquid crystal display device according to thethird comparative example, no tile-shaped pattern was observed. However,when the brightness was measured while a white display was beingperformed on this liquid crystal display device, it was found that thebrightness decreased by approximately 10% in comparison with the liquidcrystal display device according to the second comparative example.

First Example

A liquid crystal display device having picture element electrodes asshown in FIG. 11 was manufactured. In the case of the liquid crystaldisplay device according to the first example, the thickness d of theliquid crystal layer was 4 μm, the width L of each of the microelectrodeparts was 6 μm, and the width S of each of the slits was 3 μm. In thisoccasion, L+d−S took on 7 μm, and satisfied the equation (1). When adisplay was performed with middle gray-scale on the entire surface ofthe liquid crystal display device according to the first example, notile-shaped pattern was observed. In addition, when the brightness wasmeasured while a white display was being performed on this liquidcrystal display device, it was found that the brightness was improved byapproximately 7% in comparison with the liquid crystal display deviceaccording to the third comparative example.

Second Example

A liquid crystal display device having picture element electrodes asshown in FIG. 12 was manufactured. In the case of the liquid crystaldisplay device according to the second example, the thickness d of theliquid crystal layer was 4 μm, the width L of each of the microelectrodeparts was 6 μm, and the width S of each of the slits was 3 μm. In thisoccasion, L+d−S took on 7 μm, and satisfied the equation (1). When adisplay was performed with middle gray-scale on the entire surface ofthe liquid crystal display device according to the second example, notile-shaped pattern was observed. In addition, when the brightness wasmeasured while a white display was being performed on this liquidcrystal display device, it was found that the brightness was improved byapproximately 7.1% in comparison with the liquid crystal display deviceaccording to the third comparative example.

Third Example

A liquid crystal display device having picture element electrodes asshown in FIG. 13 was manufactured. In the case of the liquid crystaldisplay device according to the third example, the thickness d of theliquid crystal layer was 4 μm, the width L of each of the microelectrodeparts was 6 μm, and the width S of each of the slits was 3 μm. In thisoccasion, L+d−S took on 7 μm, and satisfied the equation (1). When adisplay was performed with middle gray-scale on the entire surface ofthe liquid crystal display device according to the third example, notile-shaped pattern was observed. In addition, when the brightness wasmeasured while a white display was being performed on this liquidcrystal display device, the brightness was improved by approximately7.1% in comparison with the liquid crystal display device according tothe third comparative example.

Through comparison of the first to the third examples with the first tothe third comparative examples, it was confirmed that the liquid crystaldisplay devices according to this embodiment were effective forimproving the display quality, and that the transmittance to be observedwhile a white display was being performed was so high that the liquidcrystal display device was effective in saving power consumption.

Seventh Embodiment

Hereinafter, descriptions will be provided for a seventh embodiment ofthe present invention.

In the case of the liquid crystal display device according to the firstembodiment, the aperture ratio can be made larger, since the liquidcrystal display device does not include structural components such asprotrusions and wide slits. If, however, the auxiliary capacitance werenot sufficiently large relative to the picture element capacitance,voltage to be applied to the liquid crystal decreases to a large extentin a frame period (approximately 16.7 ms). Accordingly, thetransmittance intensity is saturated before it reaches its peak. This isa phenomenon which is termed as a two-step response. In a case where thetransmission intensity is saturated while it is less than or equal to90% due to a two-step response, even if the liquid crystal were causedto rise sharply, a speed at which the liquid crystal panel responds cannot be increased. With this taken into consideration, in the case ofthis embodiment, a capacitance value of the auxiliary capacitance isintended to be increased while the aperture ratio is being maintained,thereby solving the aforementioned problems. Specific descriptions willbe provided for the present invention with reference to FIGS. 14 and 15.

FIG. 14 is a plan view showing one picture element in a liquid crystaldisplay device according to the seventh embodiment of the presentinvention. FIG. 15 is a cross-sectional view taken along the I-I line inFIG. 14. Incidentally, an illustration of a polarizing plate is omittedin FIG. 14.

On a TFT substrate 310, a plurality of gate bus lines 312 extending inthe horizontal direction (X-axis direction) and a plurality of data buslines 317 extending in the perpendicular direction (Y-axis direction)are formed as shown in FIG. 14. Picture element regions are defined bythe gate bus lines 312 and the data bus lines 317, and are shaped like arectangle. In the center of each of the picture element regions, anauxiliary capacitance bus line 313 is formed so as to be in parallelwith the gate bus line 312.

In each of the picture element regions, auxiliary capacitance lowerelectrodes 313 a and 313 c, a TFT 318, an auxiliary capacitanceelectrode 319 b, control electrodes 319 a and 319 c, and a first to athird sub picture element electrodes 321 a to 321 c are formed. Theauxiliary capacitance lower electrodes 313 a and 313 c are formed so asto be in parallel with a center line of the picture element region, thecenter line being in parallel with the Y axis. The auxiliary capacitancelower electrodes 313 a and 313 c are electrically connected with theauxiliary capacitance bus line 313.

With regard to the TFT 318, a part of the gate bus line 312 is used asthe gate electrode. A drain electrode 318 a and a source electrode 318 bare arranged to be opposed to each other with the gate bus line 312interposed therebetween.

The control electrodes 319 a and 319 c are formed in positionsrespectively opposite to the auxiliary capacitance lower electrodes 313a and 313 c with a first insulating film 314 interposed therebetween.The control electrodes 319 a and 319 c are electrically connected withthe drain electrode 318 a. In addition, the auxiliary capacitanceelectrode 319 b is formed so as to be opposite to the auxiliarycapacitance bus line 313 with the first insulating film 314 interposedtherebetween. The auxiliary capacitance electrode 319 b is electricallyconnected with the control electrodes 319 a and 319 c. An auxiliarycapacitance is constituted of: a group consisting of the auxiliarycapacitance bus line 313 as well as the auxiliary capacitance lowerelectrodes 313 a and 313 c; a group consisting of the auxiliarycapacitance electrode 319 b as well as the control electrodes 319 a and319 c; and the first insulating film 314 between the two groups.

The sub picture element electrodes 321 a to 321 c are formed of atransparent conductive material such as ITO, and are arranged, on asecond insulating film 320, along the data bus line 317. As shown inFIG. 14, the sub picture element electrode 321 a (capacitively-coupledpicture element electrode) is arranged in a range upper in the Y axisdirection of the picture element region, and is divided into two fields(domain control fields) with a center line in parallel with the Y axisdefined as the boundary. In addition, slits 322 extending in a directionat an angle of 45 degrees to the X axis are formed in the right field.Slits 322 extending in a direction at an angle of 135 degrees to the Xaxis are formed in the left field. This sub picture element electrode321 a is capacitively coupled to the control electrode 319 a through thesecond insulating film 320.

The sub picture element electrode 321 b (directly-connected pictureelement electrode) is arranged in the center of the picture elementregion. The sub picture element electrode 321 b is divided into fourfields (domain control fields) with a center line in parallel with the Xaxis and with a center line in parallel with the Y axis defined as theboundaries. Slits 322 extending in a direction at an angle of 45 degreesto the X axis are formed in the upper right field. Slits 322 extendingin a direction at an angle of 135 degrees to the X axis are formed inthe upper left field. Slits 322 extending in a direction at an angle of225 degrees to the X axis are formed in the lower left field. Slits 322extending in a direction at an angle of 315 degrees to the X axis areformed in the lower right field. This sub picture element electrode 321b is electrically connected to the auxiliary capacitance electrode 319 bthrough a contact hole 320 a.

The sub picture element electrode 321 c (capacitively-coupled pictureelement electrode) is arranged in a range lower in the Y axis directionof the picture element region, and is divided into two fields (domaincontrol fields) with a center line in parallel with the Y axis definedas the boundary. In addition, slits 322 extending in a direction at anangle of 315 degrees to the X axis are formed in the right field. Slits322 extending in a direction at an angle of 225 degrees to the X axisare formed in the left field. This sub picture element electrode 321 cis capacitively coupled to the control electrode 319 c through thesecond insulating film 320.

Hereinbelow, further detailed descriptions will be provided forstructures respectively of the TFT substrate 310 and an opposingsubstrate 330 with reference to the plan view of FIG. 14 and thecross-sectional view of FIG. 15.

The gate bus line 312, the auxiliary capacitance bus line 313 and theauxiliary capacitance lower electrodes 313 a and 313 c are formed on aglass substrate 311 which constitutes the base of the TFT substrate 310.The gate bus line 312, the auxiliary capacitance bus line 313 and theauxiliary capacitance lower electrodes 313 a and 313 c aresimultaneously formed through patterning a metallic film, into which,for example, Al and Ti are laminated, by use of a photolithographyprocess.

The first insulating film (gate insulating film) 314, made of SiO₂, SiNor the like, is formed over the gate bus line 312, the auxiliarycapacitance bus line 313, as well as the auxiliary capacitance lowerelectrodes 313 a and 313 c. A semiconductor film (amorphous silicon orpolysilicon film) 315, which constitutes an active layer of the TFT 318,is formed in a predetermined area in the first insulating film 314. Achannel protecting film 316 made of SiN or the like is formed on thesemiconductor film 315. The drain electrode 318 a and the sourceelectrode 318 b of the TFT 318 are formed respectively on the two sidesof the channel protecting film 316.

The data bus line 317 and the auxiliary capacitance electrode 319 b aswell as the control electrodes 319 a and 319 c are formed on the firstinsulating film 314. The data bus line 317 is connected to the sourceelectrode 318 b of the TFT 318. The control electrodes 319 a and 319 care connected to the drain electrode 318 a of the TFT 318. As shown inFIG. 15, the auxiliary capacitance electrode 319 b is formed in aposition opposite to the auxiliary capacitance bus line 313 with thefirst insulating film 314 interposed therebetween. The control electrode319 a is formed in a position opposite to the auxiliary capacitancelower electrode 313 a with the first insulating film 314 interposedtherebetween. The control electrode 319 c is formed in a positionopposite to the auxiliary capacitance lower electrode 313 c with thefirst insulating film 314 interposed therebetween.

The data bus line 317, the drain electrode 318 a, the source electrode318 b and the auxiliary capacitance electrode 319 b as well as thecontrol electrodes 319 a and 319 c are simultaneously formed throughpatterning a metallic film, into which, for example, Ti, Al and Ti arelaminated, by use of a photolithography process.

The second insulating film 320 made, for example, of SiN is formed overthe data bus line 317, the drain electrode 318 a, the source electrode318 b and the auxiliary capacitance electrode 319 b as well as thecontrol electrodes 319 a and 319 c. The sub picture element electrodes321 a to 321 c are formed on the second insulating film 320. Asdescribed above, the sub picture element electrodes 321 a to 321 c arerespectively provided with the slits 322 extending in the respectivedirections oblique to the X axis. In the case of this embodiment, thewidth of each of the slits 322 provided to the sub picture elementelectrodes 321 a to 321 c is 3.5 μm, and the width of a conductivematerial portion (microelectrode part) between each two neighboringslits 322 is 6 μm.

The sub picture element electrode 321 a is capacitively coupled to thecontrol electrode 319 a through the second insulating film 320. The subpicture element electrode 321 b is electrically connected to theauxiliary capacitance electrode 319 b through the contact hole 320 a,which has been formed in the second insulating film 320. The sub pictureelement electrode 321 c is capacitively coupled to the control electrode319 c through the second insulating film 320.

A vertical alignment film (not illustrated) made of polyimide or thelike is formed on the sub picture element electrodes 321 a to 321 c.

On the other hand, black matrices 332, color filters 333 and a commonelectrode 334 are formed on a glass substrate 331 (underneath the glasssubstrate 331 in FIG. 15) which constitutes the base of the opposingsubstrate 330.

The black matrix 332 is made, for example, of black resin or a metalsuch as Cr, and is arranged in a position opposite to the gate bus line312, the data bus line 317, the auxiliary capacitance bus line 313 andthe TFT 318 on the TFT substrate 310. Color filters 333 are classifiedinto three types, such as red, green and blue. A color filter with anyone of the three colors is arranged in each of the picture elementregions.

The common electrode 334 is formed of a transparent conductive materialsuch as ITO, and is arranged on the color filter 333 (on the lower sideof the color filter 333 in FIG. 15). A vertical alignment film (notillustrated) made of polyimide or the like is formed on the commonelectrode 334 (on the lower side of the common electrode 334 in FIG.15).

A liquid crystal layer 340 is arranged between the TFT substrate 310 andthe opposing substrate 330. The liquid crystal layer 340 is made ofliquid crystal with negative dielectric anisotropy which is containedbetween the TFT substrate 310 and the opposing substrate 330. A polymeris formed in the liquid crystal layer 340, the polymer determiningdirections in which liquid crystal molecules are aligned when voltage isapplied. This polymer is formed in the following process. A polymercomponent (a monomer such as diacrylate) is added to the liquid crystal.Then, beams of ultraviolet light are irradiated to the polymer componentwhile voltage is applied between the common electrode 334 and each ofthe sub picture element electrodes 321 a to 321 c. Thereby, the polymercomponent is polymerized into the polymer.

It should be noted that, in the case of this embodiment, the liquidcrystal with negative dielectric anisotropy is used. If liquid crystalwith positive dielectric anisotropy were used instead, the liquidcrystal molecules are aligned in parallel with the surfaces respectivelyof the substrates while no voltage is being applied. This hindersapplied voltage from being made larger when the polymer component isintended to be polymerized. Accordingly, this makes it difficult for thealignment directions of the liquid crystal molecules to match thedirections in which the slits extend.

In the case of this embodiment, the auxiliary capacitance lowerelectrodes 313 a and 313 c as well as the control electrodes 319 a and319 c are arranged in an area along a boundary between neighboringdomain control fields which are different from each other in alignmentdirection of liquid crystal molecules, or in an area where light is nottransmitted. This arrangement enables the auxiliary capacitance to bemade larger without decreasing the aperture ratio. On the contrary, thewidths respectively of the auxiliary capacitance bus line 313 and theauxiliary capacitance electrode 319 b may be made smaller in response tothe capacitance constituted of the auxiliary capacitance lowerelectrodes 313 a and 313 c as well as the control electrodes 319 a and319 c. In this case, the aperture ratio can be increased while thecapacitance value of the auxiliary capacitance is being maintained.

FIG. 16 is a diagram showing a relationship between a picture elementcapacitance ratio (a ratio of the auxiliary capacitance to the pictureelement capacitance) and a voltage ratio with the picture elementcapacitance ratio and the voltage ratio represented respectively by thehorizontal axis and the vertical axis. Note that, in this case, 4 μm isthe thickness (cell gap) of the liquid crystal layer; 0.33 μm is thethickness of the first insulating film between a group of the auxiliarycapacitance bus line and the auxiliary capacitance lower electrodes anda group of the auxiliary capacitance electrode and the controlelectrodes; −3.5 is a variation Δ∉ in conductivity of the liquidcrystal; and 53% is the aperture ratio. In addition, the voltage ratiorepresents a ratio of a write-in voltage during a white display tovoltage which is applied to the liquid crystal layer. The write-involtage during the white display is set at 1.

In this case, with regard to the auxiliary capacitance of the liquidcrystal display device according to the first embodiment as shown inFIG. 3, its picture element capacitance ratio was 1.5. On the otherhand, with regard to the auxiliary capacitance of the liquid crystaldisplay device according to this embodiment, its picture elementcapacitance ratio was 2.5. With regard to the liquid crystal displaydevice according to the first embodiment, when the picture elementcapacitance ratio was converted to a ratio of voltage to be applied tothe liquid crystal, the voltage ratio was 0.92. With regard to theliquid crystal display device according to this embodiment, when thepicture element capacitance ratio was converted to a ratio of voltage tobe applied to the liquid crystal, the voltage ratio was 0.94. It hasbeen already found that, in a case where the voltage ratio becamesmaller than a voltage ratio which caused the transmission intensity tomeasure 90%, even if the liquid crystal molecules rose sharply, theresponse speed of the liquid crystal panel did not increase. The voltageratio which caused the transmission intensity to measure 90% affectednot only the optical characteristics of the liquid crystal but also thealignment uniformity of the liquid crystal molecules. In each of thecases of the liquid crystal display devices according to the first andthe seventh embodiments, its respective voltage ratio which caused thetransmission intensity to measure 90% was 0.93. It has been learnedthrough these that the liquid crystal display device according to thisembodiment had preferable response characteristics.

The liquid crystal display device according to the first embodiment andthe liquid crystal display device according to this embodiment wereactually manufactured, and their respective response speeds weremeasured. In other words, for each of the two liquid crystal displaydevices, a rise time (τr) in which the transmission intensity rose from10% to 90% was measured, and a fall time (τf) in which the transmissionintensity fell from 90% to 10% was measured. Then, a response speeddefined by summation of the rise time and the fall time was measured. Asa result of the measurements, it was proved that a response speed of theliquid crystal display device according to the first embodiment was 20ms whereas a response speed of the liquid crystal display deviceaccording to this embodiment was as short as 12 ms.

Eighth Embodiment

Hereinbelow, descriptions will be provided for an eighth embodiment ofthe present invention.

In the case of the aforementioned liquid crystal display deviceaccording to the seventh embodiment, the voltage which is applied to thesub picture element electrode 321 b directly connected to the TFT 318 isdifferent from the voltage which is applied to the sub picture elementelectrodes 321 a and 321 c connected to the TFT 318 though capacitivecoupling. This causes electric potential difference between the subpicture element electrode 321 b and each of the sub picture elementelectrodes 321 a and 321 c. This electric potential difference causesthe alignment direction of the liquid crystal molecules between the subpicture element electrode 321 b and the sub picture element electrode321 a as well as the alignment direction of the liquid crystal moleculesbetween the sub picture element electrode 321 b and the sub pictureelement electrode 321 c to deviate respectively from the directions inwhich the slits 322 extend. A phenomenon of this kind is termed as anazimuth deviation (or a φ deviation). If the azimuth deviation occurred,the birefringence of the liquid crystal decreases locally. This causes adark line to occur. This is a cause for decreasing the lighttransmittance.

FIG. 17 is a diagram showing transmittance characteristics and alignmentcharacteristics in the case of the liquid crystal display deviceaccording to the seventh embodiment. In FIG. 17, reference numeral 2denotes an auxiliary capacitance lower electrode (corresponding to theauxiliary capacitance lower electrodes 313 a and 313 c in FIG. 14); 4, acontrol electrode (corresponding to the control electrodes 319 a and 319c in FIG. 14); 1, a sub picture element electrode connected to the TFT(corresponding to the sub picture element electrode 321 b in FIG. 14);and 3, a sub picture element electrode capacitively coupled to thecontrol electrode 4 (corresponding to the sub picture element electrodes321 a and 321 c in FIG. 14).

As shown in FIG. 17, an electric potential difference occurs between thesub picture element electrodes 1 and 3. This causes a phenomenon (anazimuth deviation) where the alignment directions of liquid crystalmolecules deviate from the directions in which the slits extend. Inaddition, portions where the respective azimuth deviations occur turninto dark lines since the birefringence of the liquid crystal decreasesin each of the portions. In the case of the liquid crystal displaydevice according to the seventh embodiment, as indicated by referencenumeral 9 in FIG. 17, dark lines occur respectively on the two sides(portions encompassed respectively by dashed lines in the right diagramin FIG. 17) of the microelectrode part in an edge of the sub pictureelement electrode 3 (a microelectrode part which is the closest to thesub picture element electrode 1).

With this taken into consideration, in the case of this embodiment, thedark lines are inhibited from occurring between the sub picture elementelectrode directly connected to the TFT and each of the sub pictureelement electrodes capacitively coupled to the TFT. This enables thesubstantial aperture ratio to be improved. Hereinbelow, specificdescriptions will be provided for this embodiment with reference to FIG.18.

FIG. 18 is a plan view showing a picture element in a liquid crystaldisplay device according to the eighth embodiment of the presentinvention. Incidentally, if components and equivalents in FIG. 18 werethe same as, or similar to, those in FIG. 14, the components andequivalents in FIG. 18 are denoted by the same reference numerals andsymbols as those in FIG. 14 are. Thus, detailed descriptions will beomitted for the same, or similar, components and equivalents in FIG. 18.

In the case of this embodiment, a group of an auxiliary capacitancelower electrode 341 and a control electrode 345 is arranged under anarea between a sub picture element electrode 321 b directly connected toa TFT 318 and a sub picture element electrode 321 a capacitively coupledto a control electrode 319 a. The other group of an auxiliarycapacitance lower electrode 341 and a control electrode 345 is arrangedunder an area between the sub picture element electrode 321 b directlyconnected to the TFT 318 and a sub picture element electrode 321 ccapacitively coupled to a control electrode 319 c. The auxiliarycapacitance lower electrode 341 is formed so as to be in parallel witheach of the slits 322 in the vicinity of the auxiliary capacitance lowerelectrode 341, and is connected to auxiliary capacitance lowerelectrodes 313 a and 313 c. In addition, the control electrodes 345 areformed in the respective positions opposite to the auxiliary capacitancelower electrodes 341 with a first insulating film interposedtherebetween, and are connected respectively to the control electrodes319 a and 319 c.

As described above, in the case of the liquid crystal display deviceaccording to this embodiment, one control electrode 345, whose voltageis equal to that of a drain electrode 318 a of the TFT 318, is formedunder the area between the sub picture element electrode 321 b and thesub picture element electrode 321 a. The other control electrode 345,whose voltage is equal to that of the drain electrode 318 a of the TFT318, is formed under the area between the sub picture element electrode321 b and the sub picture element electrode 321 c. Accordingly, oneelectric field in the horizontal direction occurs between the subpicture element electrode 321 b and the sub picture element electrode321 a. The other electric field in the horizontal direction occursbetween the sub picture element electrode 321 b and the sub pictureelement electrode 321 c. One electric field in oblique directions occursbetween the sub picture element electrode 321 a and the controlelectrode 345. The other electric field in oblique directions occursbetween the sub picture element electrode 321 c and the controlelectrode 345.

Electric field intensity (electric field density) is in proportion to anelectric potential difference and a distance between electrodes. Inaccordance with this law, influence which each of the electric fields inthe oblique directions has on the liquid crystal molecules is largerthan influence which each of the electric fields in the horizontaldirection has on the liquid crystal molecules, while the intervalbetween the sub picture element electrode 321 b and each of the subpicture element electrodes 321 a and 321 c is 3.5 μm (equal to the widthof each of the slits 322); and the thickness of the insulating filmbetween the control electrode 345 and each of the sub picture elementelectrodes 321 a and 321 c is 0.33 μm. Accordingly, only in one (the oneside being opposite to the sub picture element electrode 321 b) of thetwo sides of microelectrode parts, which are the extremities of the subpicture element electrodes 321 a and 321 c, do dark lines occur. Thisimproves the substantial aperture ratio.

FIG. 19 is a diagram showing transmittance characteristics and alignmentcharacteristics in the case of the liquid crystal display deviceaccording to this embodiment. If components and equivalents in FIG. 19were the same as those in FIG. 17, the components and equivalents inFIG. 19 are denoted by the same reference numerals as those in FIG. 17are. In the case of the liquid crystal display device according to thisembodiment, only in one of the two sides of the microelectrode part (aside encompassed by a dashed line in FIG. 19), which was an edge of thesub picture element electrode 3, did a dark line occur, as shown in FIG.19. Through comparing FIG. 19 with FIG. 17, it is learned that theliquid crystal display device according to this embodiment has animproved substantial aperture ratio in comparison with the liquidcrystal display device as shown in FIG. 17.

Furthermore, the liquid crystal display device according to thisembodiment has larger auxiliary capacitance than that according to theseventh embodiment, since the auxiliary capacitance lower electrodes 341are formed respectively under the control electrodes 345. This bringsabout an advantage of further reducing the response time of the liquidcrystal panel.

As shown in FIG. 20, the widths respectively of the auxiliarycapacitance bus line 313 and the auxiliary capacitance electrode 319 bmay be made smaller in response to a capacitance constituted of thecontrol electrodes 345 and the auxiliary capacitance lower electrode341. The smaller widths respectively of the auxiliary capacitance busline 313 and the auxiliary capacitance electrode 319 b brings aboutanother advantage of further improving the substantial aperture ratio.

In the case of the liquid crystal display device as shown in FIG. 18,when the picture element capacitance ratio was converted into a ratio ofvoltage to be applied to liquid crystal, the voltage ratio was 0.96. Inthe case of the liquid crystal display device as shown in FIG. 20, whenthe picture element capacitance ratio was converted into a ratio ofvoltage to be applied to liquid crystal, the voltage ratio was 0.94. Inaddition, the liquid crystal display devices respectively as shown inFIGS. 18 and 20 were actually manufactured, and their respectiveresponse speeds were measured. As a result of the measurement, 10 ms wasthe response speed of the liquid crystal display device as shown in FIG.18, and 12 ms was the response speed of the liquid crystal displaydevice as shown in FIG. 20.

Ninth Embodiment

FIG. 21 is a plan view showing a picture element of a liquid crystaldisplay device according to a ninth embodiment of the present invention.If components and equivalents in FIG. 21 were the same as, or similarto, those in FIG. 18, the components and equivalents in FIG. 21 aredenoted by the same reference numerals and symbols as those in FIG. 18are. Thus, detailed descriptions will be omitted for the same, orsimilar components and equivalents in FIG. 21.

In the case of this embodiment, a sub picture element electrode 351 a isformed between a sub picture element electrode 321 b (adirectly-connected picture element electrode) and a sub picture elementelectrode 321 a (a capacitively-coupled picture element electrode). Asub picture element electrode 351 b is formed between the sub pictureelement electrode 321 b (the directly-connected picture elementelectrode) and a sub picture element electrode 321 c (acapacitively-coupled picture element electrode). The sub picture elementelectrodes 351 a and 351 b are formed of ITO, in common with the subpicture element electrodes 321 a to 321 c. In addition, the sub pictureelement electrodes 351 a and 351 b extend in the same direction asmicroelectrode parts of the sub picture element electrodes 321 a to 321c adjacent to the sub picture element electrodes 351 a and 351 b extend.

A group of an auxiliary capacitance lower electrode 341 and a controlelectrode 345 is formed in an area between the sub picture elementelectrode 351 a and the sub picture element electrode 321 a. The othergroup of an auxiliary capacitance lower electrode 341 and a controlelectrode 345 is formed in an area between the sub picture elementelectrode 351 b and the sub picture element electrode 321 c. Inaddition, the sub picture element electrode 351 a is capacitivelycoupled to control electrodes (control electrodes 319 a and 345) througha second insulating film. The sub picture element electrode 351 b iscapacitively coupled to control electrodes (control electrodes 319 c and345) through the second insulating film. In the case of this embodiment,a capacitance between a sub picture element electrode 351 and acorresponding control electrode is designed to be larger. Accordingly,voltage which is larger than that to be applied to the control electrode321 a is applied to the sub picture element electrode 351 a. Voltagewhich is larger than that to be applied to the control electrode 321 cis applied to the sub picture element electrode 351 b. In other words,in the case of this embodiment, voltage applied to the control electrode321 b is larger than voltage applied to the control electrodes 351 a and351 b, which is larger than voltage applied to the control electrodes321 a and 321 c.

As described above, in the case of this embodiment, an electricpotential difference between neighboring sub picture element electrodesis smaller when the sub picture element electrode 351 is present thanwhen the sub picture element electrode 351 is absent. This furtherinhibits a dark line from occurring due to an azimuth deviation.

FIG. 22 is a diagram showing transmittance characteristics in the caseof the liquid crystal display device according to this embodiment. Ifcomponents and equivalents in FIG. 22 were the same as those in FIG. 19,the components in FIG. 22 are denoted by the same reference numerals asthose in FIG. 19 are. Through comparing FIG. 22 and FIG. 19, it islearned that the liquid crystal display device according to thisembodiment has a further improved substantial aperture ratio than theliquid crystal display device as shown in FIG. 19.

With regard to the liquid crystal display device according to thisembodiment, when the picture element capacitance ratio was converted toa ratio of voltage to be applied to the liquid crystal, the voltageratio was 0.94. In addition, the liquid crystal display device accordingto this embodiment was actually manufactured, and its response speed wasmeasured. As a result of the measurement, the response speed was 12 ms.

Tenth Embodiment

Hereinbelow, descriptions will be provided for a tenth embodiment of thepresent invention.

In the case of the liquid crystal display device as shown in FIG. 1, asdescribed above, the alignment of the liquid crystal molecules is putout of order in the base end and the extremity of each of the slits whenvoltage is applied. This is a cause of deteriorating the substantialaperture ratio. In addition, if each of the microelectrode parts wereextended toward a position near the corresponding data bus line, thesubstantial aperture ratio can be improved.

FIGS. 23A and 24A are diagrams respectively showing a light transmissioncondition to be observed when voltage is applied in the case of a liquidcrystal display device in which an interval between a microelectrodepart and a data bus line is 7 μm. FIGS. 23B and 24B are diagramsrespectively showing a light transmission condition to be observed whenvoltage is applied in the case of a liquid crystal display device inwhich an interval between a microelectrode part and a data bus line is 5μm. FIGS. 23A and 23B are diagrams respectively showing a lighttransmission condition to be observed when voltage is applied in thecase of a liquid crystal display device having no black matrices (BM).FIGS. 24A and 24B are diagrams respectively showing a light transmissioncondition to be observed when voltage is applied in the case of a liquidcrystal display device having black matrices (BM). In each of the liquidcrystal display devices, the width of its microelectrode part was 6 μm,and the width of its slit was 3.5 μm.

From each of FIGS. 23A and 23B, it was learned that a dark portionoccurred due to alignment disorder of liquid crystal molecules in an endportion of the microelectrode part. In addition, through comparing FIG.23A with FIG. 23B, it was learned that an area representing the darkportion was smaller when the interval between the microelectrode partand the data bus line was made small. In the case of an actual liquidcrystal display device, a space between a microelectrode part and acorresponding data bus line is covered with a black matrix, as shown inFIGS. 24A and 24B. When brightness of the liquid crystal display deviceas shown in FIG. 24A was measured, it was 170 cd/m². When brightness ofthe liquid crystal display device as shown in FIG. 24B was measured, itwas 181 cd/m².

If, as described above, each of the microelectrode parts were extendedto a position near the data bus line, and a space between each of themicroelectrode parts and the data bus line were covered with the blackmatrix, the substantial aperture ratio of the liquid crystal displaydevice can be made larger, and the brightness of it can be improved.However, if an interval between each of the microelectrode parts and thedata bus line were made further smaller, this causes deterioration inthe display quality due to a crosstalk.

FIGS. 25A and 25B are diagrams respectively showing results of examiningtransition characteristics of two liquid crystal display devices from atime when voltages were applied to their respective liquid crystals tilla time when alignment of their respective liquid crystals became stableby use of a high-speed camera. Incidentally, FIG. 25A shows transitioncharacteristics of the liquid crystal display device with linearpolarizing plates arranged respectively on the two sides of its liquidcrystal panel. FIG. 25B shows transition characteristics of the liquidcrystal display device with circular polarizing plates (a linearpolarizing plate+a ¼ wavelength plate) arranged respectively on the twosides of its liquid crystal panel. In the case of each of the two liquidcrystal display devices, the interval between each of the microelectrodeparts and the data bus line was 7 μm, the width of each of themicroelectrode parts was 6 μm, and the width of each of the slits was3.5 μm. In the case of a normal liquid crystal display device, 16.7 mswas one frame.

Through FIGS. 25A and 25B, it was learned that, if the circularpolarizing plate were used, the brightness and the response speed wereable to be improved. However, the circular polarizing plate is expensivein comparison with the linear polarizing plate. In some cases, thecircular polarizing plate may not be used depending on an intended useof the liquid crystal display device. From FIG. 25A, it was learned thatit took longer time for liquid crystal molecules in the base end and theextremity of each of the slits to become stable in terms of theiralignment.

With this taken into consideration, in the case of this embodiment, thebrightness and the response characteristics of the liquid crystaldisplay device is increased by improving the alignment of the liquidcrystal molecules in the base end and the extremity of each slits of thepicture element electrodes. Detailed descriptions will be provided forthe liquid crystal display device according to this embodiment withreference to the below-mentioned examples 1 to 4.

It should be noted that, in the case of each of the following examples,if a film made of a dielectric material were formed so as to have thesame shape as each of the slits does, the film may be used instead ofthe slit. The film made of the dielectric material can control thealignment direction of the liquid crystal molecules in the same manneras the slit can. Accordingly, the film can obtain the same effect as theslit does.

First Example

FIG. 26 is a plan view showing a picture element in a liquid crystaldisplay device according to a first example of the tenth embodiment.

A gate bus line 412 extending in the horizontal direction (the X-axisdirection) and a data bus line 417 extending in the vertical direction(the Y-axis direction) are formed in a TFT substrate. An auxiliarycapacitance bus line 413 is formed so as to be in parallel with the gatebus line 412 in the center of each of the rectangular picture elementregions defined by the gate bus lines 412 and the data bus lines 417.

In each of the picture element regions, a TFT 418, a control electrode419 a, an auxiliary capacitance electrode 419 c and a picture elementelectrode 421 are formed.

With regard to the TFT 418, a part of the gate bus line 412 is used asthe gate electrode. A drain electrode 418 a and a source electrode 418 bare arranged so as to be opposite to each other with the gate bus line412 interposed therebetween. The control electrode 419 a is electricallyconnected with the drain electrode 418 a of the TFT 418. In addition,the auxiliary capacitance electrode 419 c is formed in a positionopposite to the auxiliary capacitance bus line 413 with a firstinsulating film interposed therebetween, and is electrically connectedto the drain electrode 418 a of the TFT 418 through the controlelectrode 419 a.

The picture element electrode 421 is formed of a transparent conductivematerial such as ITO, and is divided into four fields (domain controlfields) with a center line in parallel with the X axis and a center linein parallel with the Y axis defined as their boundaries. Alignmentdirections of liquid crystal molecules respectively of the four fieldsare different from one field to another. In a first field upper right,formed are slits 422 a extending in a direction at an angle of 45degrees to the X axis, slits 422 b extending in a direction at an angleof 65 degrees to the X axis, as well as slits 422 c made of acombination of slits extending in a direction at an angle of 45 degreesto the X axis and slits extending in a direction at an angle of 65degrees to the X axis. In a second field upper left, formed are slits422 d extending in a direction at an angle of 135 degrees to the X axis,slits 422 e extending in a direction at an angle of 115 degrees to the Xaxis, as well as slits 422 f made of a combination of slits extending ina direction at an angle of 135 degrees to the X axis and slits extendingin a direction at an angle of 115 degrees to the X axis. Furthermore, ina third field lower left, formed are slits 422 g extending in adirection at an angle of 225 degrees to the X axis, slits 422 hextending in a direction at an angle of 245 degrees to the X axis, aswell as slits 422 i made of a combination of slits extending in adirection at an angle of 225 degrees to the X axis and slits extendingin a direction at an angle of 245 degrees to the X axis. Moreover, in afourth field lower right, formed are slits 422 j extending in adirection at an angle of 315 degrees to the X axis, slits 422 kextending in a direction at an angle of 295 degrees to the X axis, aswell as slits 422 m made of a combination of slits extending in adirection at an angle of 315 degrees to the X axis and slits extendingin a direction at an angle of 295 degrees to the X axis.

The picture element electrode 421 is electrically connected to theauxiliary capacitance electrode 419 c through a contact hole 420 aformed in a second insulating film. The surface of the picture elementelectrode 421 is covered with a vertical alignment film made ofpolyimide or the like.

Incidentally, a dot-dashed line in FIG. 26 indicates a position of theedge of a black matrix to be formed in an opposing substrate. Theopposing substrate of the liquid crystal display device according to thefirst example has the same structure as the opposing substrate of theliquid crystal display device according to the first embodiment. Forthis reason, descriptions will be omitted for the structure of theopposing substrate of the liquid crystal display device according to thefirst example. In addition, in the case of the liquid crystal displaydevice according to the first example, a liquid crystal layer made ofliquid crystal with negative dielectric anisotropy is arranged betweenthe TFT substrate and the opposing substrate. The liquid crystal layerincludes a polymer which has been made in the following process. Apolymer component (a monomer or an oligomer) is added to the liquidcrystal. Then, beams of ultraviolet light are irradiated to the polymercomponent while voltage is applied to the liquid crystal. Thereby, thepolymer component is polymerized into the polymer. This polymerdetermines directions in which the liquid crystal molecules are alignedwhen voltage is applied.

In the case of the liquid crystal display device as shown in FIG. 1, forexample in the first field, a force which causes the liquid crystalmolecules in the vicinity of a connecting electrode part to tilt in adirection (a direction at an angle of 0 degrees) orthogonal to theconnecting electrode part is added to the liquid crystal molecules dueto a line of electric force generated by the connecting electrode part.The connecting electrode part is arranged along the center line of thepicture element electrode, which center line is in parallel with the Yaxis. In addition, a force which causes the liquid crystal molecules inthe vicinity of the connecting electrode part to tilt in a direction atan angle of degrees to the X axis is added to the liquid crystalmolecules due to the slits. As a result, the liquid crystal molecules inthe vicinity of the connecting electrode part actually tilt in adirection which makes the two forces balanced against each other. Inother words, a direction in which the liquid crystal molecules in thevicinity of the connecting electrode part tilt is a direction at anangle of smaller than 45 degrees to the X axis.

On the other hand, in the case of the liquid crystal display deviceaccording to the present example as shown in FIG. 26, for example in thefirst field, a direction in which each of the slits in the vicinity ofthe connecting electrode part extends is a direction at an angle oflarger than 45 degrees to the X axis. This enables the liquid crystalmolecules in the vicinity of the connecting electrode part to tilt in adirection at an angle of approximately 45 degrees. Accordingly, a darkportion is inhibited from occurring in the vicinity of the connectingelectrode part, and the transmittance is improved. Furthermore, sincethe alignment stability of the liquid crystal molecules in the vicinityof the connecting electrode part is improved, the responsecharacteristics are improved.

Second Example

FIG. 27 is a plan view showing a picture element of a liquid crystaldisplay device according to a second example of the tenth embodiment.The liquid crystal display device according to the second example isdifferent from the liquid crystal display device according to the firstexample as shown in FIG. 26, in that the shape of each of the slitsprovided to the picture element electrode in the liquid crystal displaydevice according to the second example is different from that in theliquid crystal display device according to the first example. Except forthe shape of each of the slits, the liquid crystal display deviceaccording to the second example has basically the same constitution asthe liquid crystal display device according to the first example. Forthis reason, if the components and equivalents in FIG. 27 were the sameas, or similar to, those in FIG. 26, the components and equivalents inFIG. 27 are denoted by the same reference numerals and symbols as thosein FIG. 26 are. Thus, detailed descriptions will be omitted for thesame, or similar components and equivalents in FIG. 27.

In the case of the liquid crystal display device according to the secondexample, a picture element electrode 441 is divided into four fields(domain control fields) with a center line in parallel with the X axisand a center line in parallel with the Y axis defined as theirboundaries, as shown in FIG. 27. Each of the fields is provided withslits 442 extending in a direction in parallel with the X axis. Whenvoltage is applied, the liquid crystal molecules in each of the fieldsare aligned in a direction towards the center of the picture elementelectrode along the slits 442. In other words, when voltage is applied,the liquid crystal molecules in the upper right and the lower rightfields tilt in a direction at an angle of 180 degrees to the X axis, andthe liquid crystal molecules in the upper left and the lower left fieldstilt in a direction at an angle of 0 degrees to the X axis.

In the case of the liquid crystal display device according to the secondexample, the number of alignment divisions is two. For this reason, theliquid crystal display device according to the second example has worseviewing angle characteristics than the liquid crystal display devicewith the four alignment divisions according to the first example.However, a direction in which the liquid crystal molecules near each ofthe extremities respectively of the slits 442 (near the data bus line)tilt agrees with the direction in which each of the slits 442 extends.This brings about an advantage of avoiding a defect in alignment whichwould otherwise occur in each of the extremities respectively of theslits 442. Moreover, alignment stability of the liquid crystal moleculesin each of the extremities respectively of the slits 442 is improved.

Third Example

FIG. 28 is a plan view showing a picture element of a liquid crystaldisplay device according to a third example of the tenth embodiment.Incidentally, the liquid crystal display device according to the thirdexample is different from the liquid crystal display device according tothe first example as shown in FIG. 26, in that the shape of each of theslits provided to the picture element electrode in the liquid crystaldisplay device according to the third example is different from that inthe liquid crystal display device according to the first example. Exceptfor the shape of each of the slits, the liquid crystal display deviceaccording to the third example has basically the same constitution asthe liquid crystal display device according to the first example. Forthis reason, if the components and equivalents in FIG. 28 were the sameas, or similar to, those in FIG. 26, the components and equivalents inFIG. 28 are denoted by the same reference numerals and symbols as thosein FIG. 26 are. Thus, detailed descriptions will be omitted for thesame, or similar components and equivalents in FIG. 28.

In the case of the liquid crystal display device according to the thirdexample, a picture element electrode 451 is divided into four fields(domain control fields) with a center line in parallel with the X axisand a center line in parallel with the Y axis defined as theirboundaries, as shown in FIG. 28. A first field upper right is providedwith slits 452 a extending in a direction at an angle of 25 degrees tothe X axis and slits 452 b extending in a direction at an angle of 45degrees to the X axis. Furthermore, a second field upper left isprovided with slits 452 c extending in a direction at an angle of 155degrees to the X axis and slits 452 d extending in a direction at anangle of 135 degrees to the X axis. In addition, a third field lowerleft is provided with slits 452 e extending in a direction at an angleof 205 degrees to the X axis and slits 452 f extending in a direction atan angle of 225 degrees to the X axis. Moreover, a fourth field lowerright is provided with slits 452 g extending in a direction at an angleof 335 degrees to the X axis and slits 452 h extending in a direction atan angle of 315 degrees to the X axis.

In the case of the third example, too, one picture element region isdivided into four fields (domain control fields) which are differentfrom one another in alignment direction of liquid crystal molecules, bythe slits provided to the picture element electrode 451. In addition,each of the fields is provided with slits extending in one of directionsrespectively at angles of 45 degrees, 135 degrees, 225 degrees and 315degrees to the X axis, and with slits extending in one of directionsrespectively at angles of 25 degrees, 155 degrees, 205 degrees and 335degrees to the X axis. Thereby, a dark portion can be inhibited fromoccurring in each of the extremities respectively of the slits (near thedata bus line) in comparison with the liquid crystal display deviceshown in FIG. 1.

Fourth Example

FIG. 29 is a plan view showing a picture element of a liquid crystaldisplay device according to a fourth example of the tenth embodiment.Incidentally, the liquid crystal display device according to the fourthexample is different from the liquid crystal display device according tothe first example as shown in FIG. 26, in that the shape of each of theslits provided to the picture element electrode in the liquid crystaldisplay device according to the fourth example is different from that inthe liquid crystal display device according to the first example. Exceptfor the shape of each of the slits, the liquid crystal display deviceaccording to the fourth example has basically the same constitution asthe liquid crystal display device according to the first example. Forthis reason, if the components and equivalents in FIG. 29 were the sameas, or similar to, those in FIG. 26, the components and equivalents inFIG. 29 are denoted by the same reference numerals and symbols as thosein FIG. 26 are. Thus, detailed descriptions will be omitted for thesame, or similar components and equivalents in FIG. 29.

In the case of the liquid crystal display device according to the fourthexample, too, a picture element electrode 461 is divided into fourfields (domain control fields) by a center line in parallel with the Xaxis and a center line in parallel with the Y axis defined as theirboundaries, as shown in FIG. 29. A first field upper right is providedwith slits 462 a. With regard to each of the slits 462 a, its portionnear the base end (near the connecting electrode part) extends in adirection at an angle of 45 degrees to the X axis, and its portion nearthe extremity (near the data bus line) extends in a direction at anangle of 25 degrees to the X axis. In addition, a second field upperleft is provided with slits 462 b. With regard to each of the slits 462b, its portion near the base end extends in a direction at an angle of135 degrees to the X axis, and its portion near the extremity extends ina direction at an angle of 155 degrees to the X axis. Furthermore, athird field lower left is provided with slits 462 c. With regard to eachof the slits 462 c, its portion near the base end extends in a directionat an angle of 225 degrees to the X axis, and its portion near theextremity extends in a direction at an angle of 205 degrees to the Xaxis. Moreover, a fourth field lower right is provided with slits 462 d.With regard to each of the slits 462 d, its portion near the base endextends in a direction at an angle of 315 degrees to the X axis, and itsportion near the extremity extends in a direction at an angle of 335degrees to the X axis.

In the case of the fourth example, too, one picture element region isdivided into four fields which are different from one another inalignment direction of liquid crystal molecules, by the slits providedto the picture element electrode 461. In addition, the extremity of eachof the slits is provided at an angle of approximately 90 degrees to thedata bus line 417.

Accordingly, a dark portion can be inhibited from occurring in theextremity of each of the slits. Furthermore, the alignment stability ofthe liquid crystal molecules in the extremity of each of the slits isimproved. Moreover, it was proved that, if the width of each of themicroelectrode parts near the data bus line were made larger as in thecase of the fourth example, this inhibits display unevenness fromoccurring due to a stepper exposure process to be performed while an ITOfilm is being patterned.

Eleventh Example

As described above, if a sub picture element electrode(directly-connected picture element electrode) directly connected to aTFT and a sub picture element electrode (capacitively-coupled pictureelement electrode) connected to the TFT through capacitive coupling wereformed in a single picture element, this can inhibit the display qualityfrom being deteriorated when the screen is viewed in an obliquedirection.

FIG. 30 is a diagram showing relationship among white display voltage, adirectly-connected picture element electrode ratio and an amount ofdifference in gamma values, which relationship is observed while thehorizontal axis represents the white display voltage, and while thevertical axis represents a ratio of an area of the directly-connectedpicture element electrode to an area of the entire picture elementelectrode (the directly-connected picture element electrode ratio). InFIG. 30, if the directly-connected picture element electrode ratio were0%, this means that the entire picture element electrode is constitutedonly of the capacitively-coupled picture element electrode. If thedirectly-connected picture element electrode ratio were 100%, this meansthat the entire picture element electrode is constituted only of thedirectly-connected picture element electrode. The amount of differencein gamma values represents an average of differences between therespective gamma values to be observed when the liquid crystal panel isviewed from the front and the respective gamma values to be observedwhen the liquid crystal panel is viewed in a direction at a polar angleof 60 degrees (in a direction at an angle of 60 degrees to the normalline of the panel). This diagram shows that, the smaller the amount ofdifference in gamma values is, the better the display quality to beobserved when the panel is viewed in an oblique direction is.

In the case of the liquid crystal display device (a conventionalexample) as shown in FIG. 1, the directly-connected picture elementelectrode ratio is 100%. For this reason, according to FIG. 30, if thewhite display voltage were 6V, the amount of difference in gamma valuesis 2. In addition, according to FIG. 30, if the directly-connectedpicture element electrode ratio were in a range of 10% to 40% and thewhite display voltage were 4V, the amount of difference in gamma valuesis less than or equal to 1. It is learned through this that the displayquality to be observed when the liquid crystal panel is viewed in anoblique direction is preferable. In this case, however, the whitedisplay voltage is lower, accordingly darkening the screen. In a casewhere the white display voltage is 6V, if the area ratio of thedirectly-connected picture element electrode were in a range of 10% to70%, this enables the display to be brighter. Concurrently, this causesthe amount of difference in gamma values to be less than 1.4.Accordingly, a relatively preferable display quality can be maintainedeven when the panel is viewed in an oblique direction. As a consequence,it is preferable that the area ratio of the directly-connected pictureelement electrode be in a range of 10% to 70%.

FIG. 31 is a plan view showing a liquid crystal display device (Part 1)according to an eleventh embodiment of the present invention. In thecase of this liquid crystal display device, the width L1 of each of themicroelectrode parts of a directly-connected picture element electrode511 b is 5 μm; the width S1 of each of the slits of thedirectly-connected picture element electrode 511 b is 3.5 μm; the widthL2 of each of the microelectrode parts of capacitively-coupled pictureelement electrodes 511 a and 511 c is 4 μm; the width S2 of each of theslits of the capacitively-coupled picture element electrodes 511 a and511 c is 3.5 μm; and a ratio of an area M of the directly-connectedpicture element electrode 511 b to an area S aggregating areasrespectively of the capacitively-coupled picture element electrodes 511a and 511 c is 5:5 (i.e. M:S=5:5).

FIG. 32 is a plan view showing a liquid crystal display device (Part 2)according to the eleventh embodiment of the present invention. In thecase of this liquid crystal display device, the width L1 of each of themicroelectrode parts of a directly-connected picture element electrode511 b is 6 μm; the width S1 of each of the slits of thedirectly-connected picture element electrode 511 b is 3.5 μm; the widthL2 of each of the microelectrode parts of capacitively-coupled pictureelement electrodes 511 a and 511 c is 4 μm; the width S2 of each of theslits of the capacitively-coupled picture element electrodes 511 a and511 c is 3.5 μm; and a ratio of an area M of the directly-connectedpicture element electrode 511 b to an area S aggregating areasrespectively of the capacitively-coupled picture element electrodes 511a and 511 c is 5:5 (i.e. M:S=5:5).

FIG. 33 is a plan view showing a liquid crystal display device (Part 3)according to the eleventh embodiment of the present invention. In thecase of this liquid crystal display device, the width L1 of each of themicroelectrode parts of a directly-connected picture element electrode511 b is 6 μm; the width S1 of each of the slits of thedirectly-connected picture element electrode 511 b is 3.5 μm; the widthL2 of each of the microelectrode parts of capacitively-coupled pictureelement electrodes 511 a and 511 c is 4 μm; the width S2 of each of theslits of the capacitively-coupled picture element electrodes 511 a and511 c is 3.5 μm; and a ratio of an area M of the directly-connectedpicture element electrode 511 b to an area S aggregating areasrespectively of the capacitively-coupled picture element electrodes 511a and 511 c is 4:6 (i.e. M:S=4:6).

FIG. 34 is a plan view showing a liquid crystal display device (Part 4)according to the eleventh embodiment of the present invention. In thecase of this liquid crystal display device, the width L1 of each of themicroelectrode parts of a directly-connected picture element electrode511 b is 6 μm; the width S1 of each of the slits of thedirectly-connected picture element electrode 511 b is 3.5 μm; the widthL2 of each of the microelectrode parts of capacitively-coupled pictureelement electrodes 511 a and 511 c is 4 μm; the width S2 of each of theslits of the capacitively-coupled picture element electrodes 511 a and511 c is 3.5 μm; and a ratio of an area M of the directly-connectedpicture element electrode 511 b to an area S aggregating areasrespectively of the capacitively-coupled picture element electrodes 511a and 511 c is 3:7 (i.e. M:S=3:7).

If the width of each of the microelectrode parts were made larger, thiscan inhibit display unevenness from occurring due to a stepper exposureprocess to be performed while the ITO film is being patterned. However,this makes weaker a force to control alignment of the liquid crystalmolecules. As shown in FIGS. 31 to 34, if the width of each of themicroelectrode parts of the directly-connected picture element electrode511 b were made larger, and concurrently if the width of each of themicroelectrode parts of the capacitively-coupled picture elementelectrodes 511 a and 511 c were made smaller, this can inhibit displayunevenness from occurring due to the stepper exposure process while theforce to control the alignment of the liquid crystal molecules is beingmaintained. In addition, if the directly-connected picture elementelectrode ratio were in a range of 10% to 70%, this makes the amount ofdifference in gamma values smaller. Accordingly, this improves thedisplay quality to be observed when the screen is viewed in an obliquedirection.

With regard to the aforementioned first embodiment (see FIG. 3),descriptions have been provided of the case where the single pictureelement is provided with the directly-connected picture elementelectrode and the capacitively-coupled picture element electrodes andaccordingly a plurality of fields whose transmittance-applied voltagecharacteristics (T-V characteristics) are different from each other areformed in the single picture element. If, however, conditions (anintensity and a wavelength of a beam of ultraviolet light, and the like)where the polymer component added to the liquid crystal is polymerizedwere changed, this also can form, in the single picture element, aplurality of fields whose transmittance-applied voltage characteristicsare different from each other.

When the polymer component added to the liquid crystal is intended to bepolymerized, conditions under which voltage is applied may be changedfor each of a red (R) picture element, a green (G) picture element and ablue (B) picture element, thereby irradiating beams of ultravioletlight. This can uniform the gamma characteristics respectively of thered (R) picture element, the green (G) picture element and the blue (B)picture element. Accordingly, this can realize a liquid crystal displaydevice whose color deviation is extremely little.

In addition, if a single picture element were provided with fields whosemonomers are polymerized under conditions different from one field toanother, a plurality of fields whose transmittance-applied voltagecharacteristics are different from one field to another can be formed inthe single picture element. Otherwise, if a single picture element wereprovided with fields which are different from one field to another insurface energy of the substrate surface and thereafter the polymercomponent added to the liquid crystal is polymerized, a plurality offields whose transmittance-applied voltage characteristics are differentfrom one field to another can be formed in the single picture element.For example, if a resin film were formed on parts of the substrate,conditions under which the monomer added to the liquid crystal ispolymerized can be changed, and the surface energy of the substratesurface can be changed.

Furthermore, if the single picture element were provided with aplurality of types of fields which are different from one another inwidth of their microelectrode parts and in the width of their slits (aline and a space), the plurality of types of fields whosetransmittance-applied voltage characteristics are different from onefield to another can be formed in the single picture element.

Furthermore, the polymer component added to the liquid crystal may bepolymerized by use of a heating process, although the polymer componentadded to the liquid crystal according to each of the aforementionedembodiments is polymerized by irradiating beams of ultraviolet light tothe polymer component. Otherwise, the polymer component may bepolymerized by use of both a process of irradiating beams of ultravioletlight to the polymer component and a process of heating the polymercomponent.

Moreover, in order to compensate an optical anisotropy of the liquidcrystal layer, an optical phase-difference film which has a slow axis ina direction in parallel with the substrate surface (the surface of theliquid crystal panel) may be arranged in the case of each of theaforementioned embodiments.

1. A substrate for a liquid crystal display comprising: a plurality ofgate bus lines extending in a first direction; a plurality of data buslines that cross said gate bus lines; a thin film transistor connectedto one of said data bus lines; a first electrode including a bodyportion and a plurality of branches extending from the body portion,wherein at least some of said branches include a first branch portion,which extends from said body portion and defines a first angle withrespect to the first direction, and a second branch portion, whichextends from said first branch portion, and which defines a second anglewith respect to the first direction, and further wherein said firstangle is greater than said second angle and both said first angle andsaid second angle are between 0° and 90°; a second electrode that iselectrically connected to the said thin film transistor and thatoverlaps at least a portion of said first electrode; and an insulationfilm between said first electrode and said second electrode.
 2. Thesubstrate according to claim 1, wherein adjacent ones of said branchesare separated from each other by a slit.
 3. The substrate according toclaim 2, wherein said slits each include a first slit portion and asecond slit portion, with a bend between said first slit portion andsaid second slit portion.
 4. The substrate according to claim 2, whereinat least a portion of at least one of said slits overlaps a portion ofsaid second electrode.
 5. The substrate according to claim 1, whereinsaid second branch portions each include a free end.
 6. The substrateaccording to claim 1, wherein said first electrode is connected to saidsecond electrode via a contact hole provided in said insulation film. 7.The substrate according to claim 1, wherein said first electrode is apicture element electrode.
 8. The substrate according to claim 1,wherein said second electrode is an auxiliary capacitance electrode. 9.The substrate according to claim 1, wherein: said first electrode is apicture element electrode; said second electrode is an auxiliarycapacitance electrode; and said picture element electrode is connectedto said auxiliary capacitance electrode via a contact hole provided insaid insulation film.
 10. The substrate according to claim 1, whereinsaid first branch portion and said second branch portion are ofapproximately equal lengths.
 11. The substrate according to claim 3,wherein said bends are each formed approximately midway between anorigin of said first slit portion and an extremity of said second slitportion.
 12. A liquid crystal display device comprising: a firstsubstrate and a second substrate which are arranged to be opposite toeach other; liquid crystal contained between the first and secondsubstrates; a plurality of gate bus lines extending in a firstdirection; a plurality of data bus lines that cross said gate bus lines;a thin film transistor connected to one of said data bus lines; a firstelectrode located on the first substrate, said first electrode includinga body portion and a plurality of branches extending from the bodyportion, wherein at least some of said branches include a first branchportion, which extends from said body portion and defines a first anglewith respect to the first direction, and a second branch portion, whichextends from said first branch portion, and which defines a second anglewith respect to the first direction, and further wherein said firstangle is greater than said second angle and both said first angle andsaid second angle are between 0° and 90°; a second electrode that iselectrically connected to the said thin film transistor and thatoverlaps at least a portion of said first electrode; and an insulationfilm between said first electrode and said second electrode.
 13. Theliquid crystal display device according to claim 12, wherein adjacentones of said branches are separated from each other by a slit.
 14. Theliquid crystal display device according to claim 13, wherein said slitseach include a first slit portion and a second slit portion, with a bendbetween said first slit portion and said second slit portion.
 15. Theliquid crystal display device according to claim 13, wherein at least aportion of at least one of said slits overlaps a portion of said secondelectrode.
 16. The liquid crystal display device according to claim 12,wherein said second branch portions each include a free end.
 17. Theliquid crystal display device according to claim 12, wherein said firstelectrode is connected to said second electrode via a contact holeprovided in said insulation film.
 18. The liquid crystal display deviceaccording to claim 12, wherein said first electrode is a picture elementelectrode.
 19. The liquid crystal display device according to claim 12,wherein said second electrode is an auxiliary capacitance electrode. 20.The liquid crystal display device according to claim 12, wherein: saidfirst electrode is a picture element electrode; said second electrode isan auxiliary capacitance electrode; and said picture element electrodeis connected to said auxiliary capacitance electrode via a contact holeprovided in said insulation film.
 21. The liquid crystal display deviceaccording to claim 12, wherein said first branch portion and said secondbranch portion are of approximately equal lengths.
 22. The liquidcrystal display device according to claim 14, wherein said bends areeach formed approximately midway between an origin of said first slitportion and an extremity of said second slit portion.